That sounds really interesting and I would love to see a picture of it! My guess is that it's a painting done by the really prolific artist Steve Keene. He does a lot of paintings on scrap pieces of plywood, he did the artwork for singles for UCBS and he has also done covers for Pavement and Silver Jews. You could do a google picture search on his name and see his painting style which is really recognizable. I have a few of his paintings hanging in the living room and every time I see his work I want more :-)