Turn the sunlight more toward sunlight rather than ambient on the slider. I ALWAYS do this, especially if I am starting from a preset atmosphere. You will find that the fir trees and ferns especially are way too ambient in their material (dang things...never like 'em). Turn down the ambience in those materials also. Also you may want to turn on depth of field in your final render and use a bit of blur on the camera...that always increases the sense of depth. And definitely reduce the amount of haze and/or fog if you think you need to, but better yet, darken the color of both (especially haze) and it will not get so bright as it goes away from the camera :). Hope this helps. Laurie