Ink and watercolors on this smooth paper of some kind.
Done for Sketchfest #45 (December 2013) but the scans were terrible until May, when I borrowed a better on. (You can see the bad scan at Sketchfest: http://www.ellenmilliongraphics.com/sket
Submitted it for a comment by a Real Live Art Director on twitter (more out of curiosity than anything; I knew it was just a rough thing), and got back this feedback: be sure the underlying drawing is good.
Fair enough. Especially since the perspective is particularly off, but not purposefully/to good effect. And the shading.