You've used 300x200. The standard format is 320x200 or 320x240. I prefer the latter because of the square aspect ratio.
You are supposed to post here if you can't improve the pic yourself. You obviously know what's wrong with it, why don't you give it a shot?
I've fixed the size and did a very sloppy paintover to fix the most glaring error: the perspective.

And, as you've mentioned youself, get rid of the textures. Textured pics tend to look unnatural and flat. Another good idea would be to dump those black outlines, especially the ones surrounding the lower stones.
You are supposed to post here if you can't improve the pic yourself. You obviously know what's wrong with it, why don't you give it a shot?
I've fixed the size and did a very sloppy paintover to fix the most glaring error: the perspective.

And, as you've mentioned youself, get rid of the textures. Textured pics tend to look unnatural and flat. Another good idea would be to dump those black outlines, especially the ones surrounding the lower stones.