These are some various colored Dirt tilesets from my current project, Atomic Alice.

The playable Beta can be found here: http://makegameshappen.deviantart.com/art/Beta-Five-437510669
Hint: currently you can skip levels with N and go back with B if you, like me, die 50 times in a row on a stage.
John has also created various fractal tools on his page some of which use these tilesets to allow the user to make their own fractal art.
Here's one of the fractal makers with another tileset I created. http://www.deviantart.com/art/AutoVentSteelWithGoldCaps-438487741

I'm making numerous 16 tile sets that connect to each other at 16x16 size. These represent different materials etc. in the game that may break or leave platforms etc.