I'd better post so this thread doesn't go too far down, it's too awesome.
I don't know if you're planning to, but I don't think you should detail the silhouette-trees too much. As it is, it's got a nice intelligible focus. maybe just an additional color to give them depth... not sure, though.
I would cast some of that red light out the door onto the leafy platforms.
It's a bit excessively green. Maybe have light of a different hue being cast from the bg - orange, or blue?
& I think it would benefit from a bit of anti-aliasing.
The way you've shaded the trees has influenced how I'm going to approach cylindrical surfaces in general now, so thanks.
