I decided to try drawing a set of octagons from scratch, and got this:

I tried making it look a little more like stones this time around rather than just octagons. Opinions?

EDIT: Also, the only reason these are green is to make it easier for me to do some of the pixel-by-pixel shading. The colour scheme can be changed whenever.

EDIT2: Getting a little carried away, but how's this for a surface?