I mentioned the lack of tree variety to the potential client too. After all, it was just a test for the structure. If I get the commission this will be a major setup, with all kinds of interesting things. More bump would be good, perhaps, but I quite like the lighting as it is. I used the EXR to produce two layers (dark and light), then subtly wiped some areas off of one layer. To concentrate the light near the labyrinth.
Nice fake IR, Ryan. I'll try that as well. The noise is a bit too much though, IMO.
The 'fortress', by the way, is supposed to be a burial monument/chamber, growing as more people die.