Good image, cool to see you can add vegitation in terragen now. I think the horizon is to flat though and everything is just a bit to much alike. The light comming at the camera from the corner is an un-needed distraction. I think this image could really really come alive with a few point lights around creating some interesting light/shaodw contrast through the trees, a volumetric light coming through the trees casting shadows off the trunks, and a touch of fog to blurr the distant horrizon and make this a much more "in-charcter" feeling image.
I feel the light balance you have now(on darker side) is good but it needs higher definition shadows and lights.