All of them basically, that's only how a tileset can look. The tilesets isn't what mainly do the KnyttWaDF graphics, it's the objects that gives each area an unique look. I know that people here are used to thinking that all graphics are built out of tiles, but it plays a much smaller role in this game than for example Knytt Stories. You don't even get layers for the tiles this time. Tilesets just define if the ground is soft, rocky, sharp, grassy, technological, and so on. However, tilesets are still very important, the player will still begin to noce if the same tiles are used all the time for everything, and small variations will prevent this. The objects at the other hand are much more powerful.
minmay: Thanks for your tileset! It's slightly tricky to use though as it doesn't use actual antialiasing but a blur, which looks different. I use two techniques to do antialiased graphics. One is simply to stick to polygon-like tools (such as Photoshop's polygonal lasso tool, line tool, or pen tool), or draw the image as pixel graphics in 3x the image size and then downsample the image to the desired tileset size.
However, all tilesets that doesn't fit perfectly within the game will go into the library, which will be a lot like Knytt Stories' library that is used by third party level designers.