I've been doing these monthly auctions on Ebay, sketching on the backs of Artist's Proofs. (An Artist's Proof is a Magic card without the corporate logo on one side. Only the artists get 'em and we don't get very many. Turns out the surface is really fun to draw on!) Here's an example of the sorts of sketches I do. This one was drawn with a gold gel pen on a ground made using warm grey Char-Pak markers.