What a fortunate group of players you have. Dank, dark, mold ridden, forgotten depths to be hazard by only the most foolhardy or desperate.

I wish I could make out a little more of what is hidden in each corner of the room but then, so do your players.

Do you use such visual aids at the beginning of a new area to present the right mood and feel or is it a reward for story completion toward the end of a chapter?