The artist drew portraits of Gallo and co-star Gary Oldman for one restaurant scene in his 1996 directorial debut, Basquiat, in which Gallo portrayed painter Francesco Clemente.
Schnabel gave both drawings to Gallo as a gift.
Now the actor is selling them on auction website eBay.com.
He tells the New York Post, "I'm building a new house in downtown L.A. (Los Angeles). I want everything to fit... I'm going through things. I don't want it, and it's too valuable to give away. I'd rather buy shoes."