Here are a pair of sketch cards that I just completed for Mike in North Carolina:
I really like how these came out. I used my Japanese Pilot pens, a Pitt brush pen and Prismacolor markers to finish them. I have not really drawn either Batman or the Hulk prior to this, although I think in some ancient sketchbooks I did when I was about 8 there are a few Batman drawings.
I've actually gotten a bit of attention for the sketch cards I did for InkWorks, which has gotten me some small side commissions like this one. I should probably do like my friend Tone Rodriguez (who got me into the sketch card game) and get some custom-printed personal sketch cards to draw on. Hopefully I'll be able to do some live at San Diego Con, too. If you like sketch cards, I'm happy to do commissions!