The sketch-tablet combination is an interesting effect - almost like it's etched... or something. The lighting suggests a church to me - high window and all that. I love how the yellow shows up against blue shadows.
Yeah, sorta was thinking it was in some warehouse, and Carrot was asking Angua why she was so upset.... I think next time I'll hold off shading with pencil on the faces- it was a bitch to color there and make it look ok!