"You were in a cameo on The Empire Strikes back weren't you?
Yes, they got the artist's together to do a scene that was played out over a Matte painting that I had done of Rebel ships parked in the Ice cave. We were going to be Rebel soldiers. I was a general who walked by from screen right to screen left. You can see me if you know what to look for. Joe Johnston, Harrison Ellinshaw and Mike Pangrazio, stood in the foreground and had a few lines, they didn't trust me with lines, they knew I would flub up (laughs)."
EDIT: Yocke beat me to it.
EDIT UPDATE: Okay I've found the scene: Its about 20 minutes into the film, and comes after vader says "set your course for the Hoth system... General Veers, prepare your men "
That's mcquarrie on the right.
I never really noticed it before, but that is a pretty dodgy matte painting of some rebel transports in the background.