Inspired by Gnomon. I painted some concepts to decide the mood and lighting for my project darkScreen. The floor and walls are taken straight out of a UE3 screenshot, so now I'm concentrating on the ceiling.

The ceiling in the concepts were sketched quickly to have it reflect light and to receive shadows. Remember this sketch was done to experiment with colors and contrast and not the elements of the scene itself, so the roof detail was not important to me, as long as it looked detailed enough. Some of them were done for fun and I spent more time on others.