With "go for it" from TigerNDV I'm starting a thread for his level. It's a medium-sized epic adventure for KS+ mod.
Download: https://knyttlevels.com/levels/TigerNDV%20-%20Above%20the%20Clouds%20v2.knytt.bin

My tip: Remember that in KS+ you can press Space+Down to save the game anywhere after you've activated cheats with Ctrl+Shift+C combination. If level's intended way of saving isn't your cup of tea, use this cheat instead, like I did.

Similar to Ctrl+X zoom found in KS Ex and KS+. Can be applied to any game made with Multimedia Fusion 2 or its predecessors that doesn't use DirectX for graphics output. Makes the game scale to whole screen without the need for resolution change. Also lets you remap keys.
I finally played Riddle with it and it was really cool.
Knytt Stories Level Editor (Ex) was the reason I've implemented Windowed mode option.

Download it here: https://grayface.github.io/ks/#Scaler-for-MMF-Games

Sadly, doesn't work for Operator Status, because it uses DirectDraw. Same goes for Level Editor Plus and Knytt Stories Simul mod. Doesn't work for Saira and Night Sky - they hang.

WaDF, first Modarchive Story, Mushroom Engine, Riddle, Knytt and its mods, Knytt Experiment, Knytt Stories and its mods KSAdvanced and ACO are all tested and working fine.

DirectDraw support may come in the future, together with better non-integer scaling. I may also implement drawing old games through DirectDraw to fix the FPS issue caused by Windows Aero aka WDM.
Compatibility with Saira and Night Sky may also come in the future, I have an idea for that.

P.S. Feel free to post it on Multimedia Fusion related forums. I was amazed at how greedy and messed up ClickTeam is, not even allowing people who didn't pay them to view some forums.

Is source code of Knytt XH available somewhere? I'd like to add borderless fullscreen to it.

A single room level I made to test falling platforms. Requires KS Ex.

Download:
https://sites.google.com/site/sergroj/ks/GrayFace%20-%20Platforms%20Room.knytt.bin

Object templates introduced in KS Ex are like an advanced version of custom objects.
In this thread I'll explain how to use and make these objects and here will be a collection of template objects for public use. Please post your objects. When you post objects here and don't tell otherwise, it is assumed that anyone is free to use and modify them as long as proper credit is given and the derivative work is non-profit and KS-related.

Using Template Objects

First, download the archive of all objects: https://www.dropbox.com/s/juvg3yygsnrj8g4/Template%20Objects.rar?dl=1
Then copy objects you want to include into Objects subfolder of your levels folder (create it if it doesn't exist).
Copy the path(s) of Ini file(s) corresponding to the object(s).
Then in the editor select an unused template object (any object in Bank 254) and press "+" near object number.
Clipboard contents are automatically pasted into the dialog, so just press OK.

How to do it manually and/or set up optional parameters:
Say, you want to use Angry Fish object in you level.

• Put the object somewhere in the world folder. For example, create Objects sub-folder and copy the "Angry Fish" folder there.
• Create [Templates] section in your World.ini file. Add this line there:

1=Objects\Angry Fish\Object.ini

• Open Bank 254 and you'll see the angry fish as the object number 1. To define object number 2 you would write "2=" instead of "1=" in [Templates] section, and so on.
• Some objects may take parameters. For example, you can change height of Angry Fish jumps by adding this line to [Templates] section:

Params1=60, 80
Now the fish will jump higher.

Objects List

Collectables

Collectable items (except new keys) can be picked up more than once, you see their count in the power bar. Note that unlike KS+ here's no index attached to each individual coin or artifact and count is not limited.
Optional parameters:
1) Set this to 'true' to show power on power bar only after the item is picked up. This is how it's done in KS+, but in my mod by default all collectables used in the level are present in power bar.
2) Allow only one instance of collectable, like with ordinary powers. By default this is 'true' for keys, 'false' for other collectables.
Authors: egomassive, GrayFace, Nifflas

Collectables - Locks

Locks for collectable items can have a number attached to them, telling how much items you need to collect to pass through. A negative number used for coins means that items count would be reduced by the number and lock would then be permanently open (that is, you pay once to open the lock).
Optional parameters:
1) Count needed to unlock. By default it's '0' for keys, which means that no count is shown on the lock and the lock acts normally. It's '5' for artifact locks, meaning that 5 artifacts are required to pass. It's '-5' for coins by default, meaning that you pay 5 coins to pass when you touch the lock.
2) Hide items count label.
Authors: GrayFace, Nifflas, egomassive

Golden Creatures

Golden creatures are living collectable items. They're almost identical to ones from KS+ with 2 exceptions: creature 32 kills you if it drops on you and creature 49 kills you if you stand still.
Optional parameters:
1) Set this to 'true' to show power on power bar only after the item is picked up. This is how it's done in KS+, but in my mod by default all collectables used in the level are present in power bar.
2) Allow only one instance of each kind of creature, like in KS+. By default this is 'true'.
Authors: egomassive, GrayFace

Golden Creatures - Locks

Locks act similar to those for collectable items. I decided to keep the count label by default, eventhough in KS+ these locks don't have it. It's intuitive this way. If you want to remove it, set the 2nd parameter to true.
Optional parameters:
1) Count needed to unlock. By default it's '0' for keys, which means that no count is shown on the lock and the lock acts normally. It's '5' for artifact locks, meaning that 5 artifacts are required to pass. It's '-5' for coins by default, meaning that you pay 5 coins to pass when you touch the lock.
2) Hide items count label.
Authors: egomassive, GrayFace

Force Keys
;
Again, all these except "Only Down" come from KS+. "Block User" fully blocks user control of Juni. Unlike in KS+, here it only works while Juni is touching it. "Only Down" blocks all control of Juni except Down key, so it's a replacement for Sticky-No Jump combination that also blocks hologram creation. The other objects force a single key when Juni is touching them.
Optional parameters of "Block User" and "Only Down":
1) Timeout after which the object releases player and possibly self-destructs.
2) Keep it alive after the timeout? "false" is default, so after the timeout the object is gone. In case of "true" you can re-enter the object and get stuck again.
Authors: GrayFace, egomassive

Map Power

Ini file:
Objects\Map Power\Object.ini
Another one from KS+. Enables you to see where you haven't been on the map.
Authors: egomassive, GrayFace

Angry Fish

Ini file:
Objects\Angry Fish\Object.ini
A fish that jumps out of water and may kill the player.
Optional parameters:
1) Width of trajectory (defaults to 50)
2) Height of jump (defaults to 60)
3) Delay between jumps (defaults to 100)
4) Gravity (defaults to 45)
Author: GrayFace

Moving Bouncer

Ini file: Objects\Moving Bouncer\Object.ini
A bouncer that moves in player's direction, like the one seen in Extended Version Example, but blue. Avoids getting stuck in a wall reasonably well.
Optional parameters:
1) Delay, the opposite of speed at which the bouncer moves right and left (defaults to 2)
Author: GrayFace

Darkness

Ini file: Objects\Darkness\Object.ini
Makes the screen dark, leaving only a circle of light around player.
Optional parameters:
1) X offset from default position of light
2) Y offset from default position of light
3) Set this parameter to 'true' to make the darkness stay in its layer. Otherwise it appears on top of everything.
Author: GrayFace

Jump-Through Platform

Ini files:
Objects\Jump-Through Platform Left\Object.ini
Objects\Jump-Through Platform Middle\Object.ini
Objects\Jump-Through Platform Right\Object.ini
Objects\Jump-Through Platform Invisible\Object.ini
A platform that doesn't prevent the player from jumping through it from below, but lets the player stand on it.
Optional parameters:
1) Relative Y coordinate of player at which the object becomes solid (defaults to -18)
Authors: GrayFace, BloxMaster

Moving Platform

Ini files:
Objects\Moving Platform\Object.ini
Objects\Moving Platform Big\Object.ini
A moving platform, jump-through by default.
Optional parameters:
1) X speed (defaults to 100)
2) Y speed (defaults to 0)
3) Hotspot X (defaults to 12)
4) Hotspot Y (defaults to 12)
5) Jump-through offset (defaults to -6, set it to 'false' to make the platform fully solid)
6) Jump-through offset with inverted gravity (defaults to 5 + 5)
7) Kills player when smashed against a wall (defaults to 'false')
Author: GrayFace

Falling Platform

Ini files:
Objects\Falling Platform Small\Object.ini
Objects\Falling Platform\Object.ini
A platform that descends while you stand on it.
Optional parameters:
1) Delay, the opposite of speed at which the platform moves down (defaults to 2)
2) Hotspot X (defaults to 12)
3) Hotspot Y (defaults to 12)
Author: GrayFace

Touch Save Spot

Ini file: Objects\Touch Save Spot\Object.ini
Save spot triggered by touch.

Ini file: Objects\Touch Save Spot\Up.ini
Upside-down save spot triggered by touch when gravity is inverted.
Optional parameters:
1) (if 'true' is passed) Trigger by Down key press, acting like a normal save spot.
Author: GrayFace

Visible Spikes

Ini files:
Objects\Visible Spikes\Spikes 1.ini
Objects\Visible Spikes\Spikes 2.ini
Objects\Visible Spikes\Spikes 3.ini
Objects\Visible Spikes\Spikes 4.ini
Spikes that are always visible. You can also call load.lua script to replace all standard spikes with ones that are always visible.
Author: GrayFace

Water Wheel

Ini file: Objects\Water Wheel\Object.ini
Solid rotating wheel.
Optional parameters:
1) Rotation speed (defaults to 1)
Author: GrayFace

Smasher

Ini file: Objects\Smasher\Object.ini
It smashes Juni if she gets caught under it. (Or if she touches it at all) It looks best when placed at the top of the screen, otherwise it looks like it's unfolding from nothing.
Author: LordMarzog

Combined Fog

Ini file: Objects\Combined Fog\Object.ini
Combination of two fog adders made by Nifflas, turned into an object.
Authors: Nifflas, GrayFace

Machine Cylinder

Ini file: Objects\Machine Cylinder\Object.ini
Semi-transparent cylinder for machine from tileset 5. To be placed above Juni
Authors: LPChip, LordMarzog, GrayFace

Machine

Ini file: Objects\Machine\Object.ini
Machine from tileset 5 turned into an object.
Authors: LPChip, GrayFace

Making Template Objects

The simplest example of template object is Combined Fog from the archive above. If your object only has one frame, you don't need a script that would load it. Here's the important part of Object.ini of Combined Fog:
[Object]
Image=Combined Fog.png
Offset X=48
Offset Y=-84"Image" is the image displayed in level editor and used in the game if no loading script is specified.
"Offset X" and "Offset Y" are image offsets, similar to corresponding fields of custom objects.
"Icon" is the image displayed in objects palette. Combined Fog doesn't have one, because it's too big to be displayed there.
"Load" is the script of the object. Combined Fog doesn't need it.
"DoesHurt=1" will make the object kill Juni when she touches it.
"DetectRed=1" will make the object trigger red light of detector.
"Solid=1" will make the object solid.
"CanClimb=1" will make the object climbable.

You can turn custom objects into template objects with this tool. You may want to use it because template objects can be made solid or dangerous for the player. There also isn't a 1 tick delay before they are shown on the screen.

Standard Objects

If you want to replace graphics of a standard object I can extract frames and generate a replacement script for you. Standard Frames archive contains scripts and graphics for some objects. It also contains a script for Juni's sound replacement (Player Sounds). Graphics of any object or in-game interface element can be replaced this way. Shape of objects changes together with graphics. Custom characters can be found in    
Custom Characters collection thread.

FTF32 has made a new level. I haven't played it yet and for me it's hard to make screenshots ATM. I'm pretty sure it will turn out a nice and really Lunatic level.
http://knyttlevels.com/levels/FTF32%20-%20Adventures%20of%20a%20ball.knytt.bin
The level requires KS Ex mod, which can be found in my signature.

Here's the second level with a ball by FTF32. You have 1000 100 fly charges instead of regular 3.
Download

This level teaches you to play KS in the ball mode and also contains a challenging Advanced difficulty mode. To play it you need to install Extended Version mod first. If you don't know what 'ball mode' I am talking about, you definitely must play it!

Both the mod and the level can be found at https://sites.google.com/site/sergroj/ks

Version 2 has two new secret endings and is updated to reflect changes in KS Ex.