Some of you have been asking about including walls in the set. I hand-drew a full page of stone wall texture that you can cut and paste to make walls as room backdrops. Cutting and fitting them is a bit tricky but they do a good job of letting you know how tall the ceiling is in a given room. I would consider them an option for more advanced builders! Note how I've shown two ways of doing cutaway walls (curvy edge and stepped).
The wall texture can double as a cliff or sheer drop, too.