I like it, very clean look, nice colors, and looks kind of cartoony.

If you're going to shadow one thing, you probably need to shadow all of it; it makes the cliffs stand out more and brings some depth to them, and wouldn't hurt to add it to the trees and rocks to add more realism.

Two things I notice about the cliffs; with the same pattern going up, and matching each section, it hurts the feeling of depth.  If you look at something like a Zelda game-A Link to the Past-you'll see there are two patterns going up, which can help to offset the 'tiled' feeling, and makes having two levels of tiles easier to display.  Also, the clifftop on the left is two tiles wide, while the base is only one tile wide.

Otherise, looks excellent, wish I could get tiles that clean and recognizable.