Hi,
in my opinion you have a little to little of everything in here

What that is supposed to mean is that:
- there are not enough distinctly sized and shaped and colored fake stones
- there are not enough trees distributed, that would be of different sizes and possibly species
- there are not any other types of vegetation, that one would expect in this scenery
- there is not enougg variation in the surface texturing and detail displacement of the terrain
The clouds are great though.
All in all I would say that this scene is a start of a potentially great scene, it just needs much more variation, complexity and detail. If you take care about that, you can make that a fantastic render.
For other examples, look at the "Explorers" image thread, or the "Riverbend" image thread, that show very clearly how great scenes usually start at a comparable level of complexity and variation, and then get refined step by step. Yours could be the next in that row.
Cheers,
Frank