I did this project some time ago with a couple of my 2nd and 3rd grade classes. I introduced them to artist David Hockney and his wonderful cubist style photography pieces. I particularly like Hockney's photo collage of his mother.
To create our inspired pieces, I took 5 close up pictures of each child's facial features. I ordered double prints so each child could put together a portrait of themself as well as a crazy mixed-up portrait using classmates features put together. It was a big hit and this piece in my house still gets a lot of laughs. The children love to try and name each of the boys in the picture.