Hey man, it looks pretty good so far. There are a couple suggestions I have for you, and a quick paintover for you to see the difference. First off, I agree with Cam that it's a bit off in the top right corner, it just feels like stuff is up there for no reason. I like the rocks in the side of the frame, but there are like two or three things that my eye gets drawn to at the same time. I think if you made most of the focus on the stuff in the middle-left, you'd have a more solid composition at this point. Also, everything is just a bit too bright really. Maybe you are going for a really stylized look, but your shadows are a bit off here and there. I did a really quick paintover, just to show what you might do to get it looking a bit more on... Hope you don't mind man...
Mine is a bit dark maybe, but you can see where I added in a bit of detail and put more darkness where it needs to be. Just for illustrative purposes.
-Z