The Tree of Knowledge [challenge/normal/large]

Like. 

Do kinda agree with Raicuparta.  The second one as its appeal.

All of those bridges have their charms, but the third one looks the nicest.

I think you should use both the second and the third version, depending on whether you want to make it solid or not.

A fine idea. These bridges are for a large city and some variety wouldn't hurt.

I've put some further work into city tiles, and I'm happy with the progress. For the entire game I have a plan to use 2 tilesets for each area. A base tileset holds all the basic elements of an area. The filler set holds additional pieces for greater variety. The best part about this is I don't have to make compromises when transitioning between areas. I simply use the base tileset from each area. The city I envision demands a great deal of inner variety, so It's a little more challenging to layout tilesets. The tactic I'm using is to put the foreground and middle-distant tiles of the city's main architectural style on the base (as seen in the bridge examples.) The base also includes the most distant buildings and city amenities like lamp posts. Then, there will be multiple filler sets which include foreground and middle-distant buildings of varying styles.

I keep having to do that same thing for my tilesets and areas.  It is exceedingly hard to get a great variety out of one tileset.  You don't get as many surprises.

Have you tried black outlining (or a darker tone) on the bridge pillars and arch?

I won't outline background stuff in black. It might look better as a static image, but being part of a game I feel it's most important to know what's solid and what isn't instantly. In the case of these bridges you normally wont interact with the support structure. But, I may want to stick something under a bridge so I'm keeping that option open.

Since we're talking about the city I'll post a tileset update. In this image you'll see the new gradient, the distant buildings, a few foreground objects, and the old middle-distant buildings have been toned down. I realized the mid-distant tiles were too busy when I started adding foreground objects. I think this version looks a ten times better. This is still a work in progress, I haven't made the mid-distant bridge arches yet.

Looking very nice.  Yeah, the buildings look a lot better.

It's looking fantastic. I think it's a really good idea to use the outlines to show which objects are solid aswell; really clear without being intrusive.

Slight rabbit trail, I had an art teacher in college that would through a fit if we outlined in black, so it is very hard for me to use the black outlines.  But I do see their function. 

Actually, I've pondered borders quite a bit while working on this level --read several articles which I can't find anymore or I'd give links. I noticed early on that I was putting bold, black borders on all the hard surfaces; while putting more subtle border on soft ones. I'm afraid the combination will be jarring, but I plan to worry about it later. By later I mean, when the level design is complete.

I experimented with semi-transparent boarders in the past, and that has some appeal.

Going by the screenshots you've posted so far, the different borders don't seem jarring to me and I'm sure they'll be even less likely to be so while playing the level. While I understand the point of Headgrinder's art teacher's opinion, that was in relation to with traditional artwork; a game has different priorities, including a clear distinction between solid objects and purely decorative.

And that clear distinction is very important, and I'm not trying to tell anyone how they should make their tileset.  But I do think there is something to be said for working towards alternatives, even if you have to shrug and say, "well, I didn't find one this time."  

Oh, of course. I certainly didn't mean to criticise or belittle your tone or input. I was only offering an opinion on the effect and I'm sorry if it came out too negative.

Oh, sorry.  I didn't mean to sound combative either.  Curse you impersonal text format!