I have done something like with the younger students and portraits of famous artists, particularly Picasso. I took a very large black and white of Picasso, cut it in half, glued it onto A4 Black paper and got the children to finish the portrait with various materials. They usually created an unconscious Cubist response which probably would have delighted the artist. They did not know who the portrait was of until after it was completed and it was usually a very good introduction to him.