My son likes tessellating designs, log cabin and bargello style. I agree that the graphic appearance is what appeals. I think anything Frank Lloyd Wright or M.C. Esher might appeal too.
http://www.mcescher.com/gallery/
://www.google.com/search?q=M.+C.+Escher+quilt&biw=1164&bih=817&source=lnms&tbm=isch&sa=X&ved=0CAcQ_AUoAmoVChMI4-aC2P6JyAIVyKKACh3rVQbI&dpr=1.1