What is with newbies and drawing hills with the sun over them? It makes shading 100x more difficult then a sprite or small object.
Okay.
-Too little contrast.
-There should be some hue variation. Also, that's a really bad green for anything, except maybe some man-made things or gems.
-Sun is too large, and too yellow. And not bright enough. Of course, this isn't really important, since using symbolism in art is perfectly fine (Except for most cases that involve anatomy).
My advice is either A) colors some line work from the line art thread or B) create a small object or sprite. If you draw a sprite make either a monster or a human with enough armor to get rid of all need for proper anatomy-drawing skills. Make sure you define a light source (Where light is coming from) before you start shading it.
Edit: That took me more than 10 minutes to write? Wow.
Also, dang you Spartacus! Er... MrNormS.