This is a personal taste thing for me. I like the colors and what you're trying to do. The tree clumps are pretty good as well, but it lacks a feeling of space and depth. This may be deliberate on your part, and that's fine. For me though, I always like to give the impression of "real space" and "real distance. I go with a very rough formula of one close object, the focus of the scene in the middle and then detail in the back to draw the viewer in. I don't always use it, but it's in the back of my mind to give the illusion of space. Also, be careful with the ambience on materials. Most times, I kill it on my materials unless the item is glowing. The shadows just don't feel real with it on. IMHO