Critique:Your textures are noisy. Rather than implying texture such as rigid, rough, smooth, furry, grainy, etc. The eye tends to pick it up as an undefinable stuff.

You haven't employed a definable light source on much of your segments. For example, your trees tend to be darker on the left and lighter on the right (implying light from the right) But your clumps of leaves are showing highlights and shades in the opposite direction (implying light from the left).

Advice Begin by picking a light source for shading.
Work on defining your textures a bit more, rather than copy pasting repeating blocks of random colors.
Consider the way in which your elements all look somewhat flat upon the screen. As if they could be picture cutouts on top of one another. Shading and highlighting properly will remedy some of this effect.