Hey people, keep it on topic or I will start deleting posts.
As for the picture, I think the perspective of the whole thing is rather confusing, the rocks look like they are on a horizontal plain, while the grass and ground look like they are on a vertical one (as if it were painted on a wall).
The coloring is nothing special right now. You could study tiles from different games and see how they do it.
Can't really tell the purpose of the picture, so I guess you can ignore this on your choice, but I would lose the black outlines on the rocks, and leave the background set back as a background.
Good luck with your next thing and hope you enjoy pixelling