Ben Wilson is an English artist best known for his unique brand of chewing gum art. That's what he's up to in that photo above; Wilson paints the dried chewing gum stuck to the ground. He's has been doing this for about ten years now and has even been arrested a couple times, though all charges were dropped when it was determined that no law forbids the painting of rubbish.
Here's a terrific Flickr album of his art.
And here are some great resources if you'd like to learn more about Ben Wilson.
Photo credit: DisillusionedBitterAndKnackered / Wikimedia Commons