First of all, I notice you are using a mix with Blizzard trees and imported ones. Replace the Blizzard trees, they just isn't doing the terrain any good. What's really ruining the imagery for me is the fact that it looks like the world just comes to a complete stop behind those shy trees in the background. Perhaps the angle isn't the best either, as you can't squeeze much of a light source in there.
Furthermore, consider where you place flowers and shrubbery. For example, the leaf tile doesn't really work with flowers on it in my oppinion.