Hi Linda,
a nice terrain you have here. The strongest points are the terrain and the sky. The clouds looks really good and convincing. Surfacing though is a challenge. I have the suspicion that the trees are too large compared to the terrain. Also, I think trees should be denser and less evenly distributed.
With surfacing, in TG2, it's better to not use a green surface layer to mimic vegetation, unless your camera is so far away that real 3D vegetation instances can no longer be seen as individual objects. Focus on surface shading the rock, a little moss here and there, sand, stones, soil, etc... then use denser populations of grass and trees and bushes and flowers to make the green.
Cheers,
Frank