I made a very small edit, I only changed 2 things; I made the walking plane abit more obvious, and I a few of the BG colors.

Things were blending in together too much in your picture, characters should be obvious, and the whole thing looked very flat; I only added one line, but it gives the player the idea that its a surface you can walk on. Theres not much of a feeling of depth; the ground looked about on the same level as the background.