Have some old ceiling tiles laying around? You might want to think about using them as ‘canvases’. That’s just what art instructor Carrie, known as orangesoc12 on Flickr did. Although, her tiles weren’t just laying around; they were actually in the ceiling of her classroom. She had her 8th grade students take them down and draw on them--using Georgia O'Keeffe for inspiration--and then they put them back up. You can see more examples of her students’ work on Carrie's photostream.