I spent some time playing with shaders and colors today. Figured out way to improve backlighting issue on the big trees, that made them look quite messy and tried some distant haze... I got to a point where I really believe I can make something cool with this :) It will require more variety, some tweaks etc. but I can start thinking about proper scene now...
So, here is the new version:
and here is older one:
and a little test with volumes: