I did some portraits of my students several years ago and had them paint the background too. light blue butcher paper, lots of acrylic paint and hands instead of paint brushes. That was a lot of fun, the images looked cool, and we all got in trouble for making a big mess. (I had no idea water based red acrylic paint was so tough to get out of carpet.). The problem was the backgrounds were temporary.

Has anyone ever painted their own more permanent background cloths? If so what did you use?