I like this lots, looks very natural. The lighting is excellent. I would disagree with njeneb about the rock colours... (mind you this is a personal taste thing

) Where you have a surface protruding rock field in real life, and there are a lot of debris (rocks, boulders etc) It is almoast certain to have come from said rockfield. In other words, most of the loose rock lying around has come from the local bedrock, and is therefore going to be the same colour range, everywhere. I think this gives your render its naturalness.
Although nature is capable of producing the most breathtaking beauty, most of it is very, very bland... admittedly, this doesn't work well for pretty TG2 renders, but it does for realistic ones, in my opinion, anyway.

Miles