Here is an article I ran across from Inhabitat.com. The images are actually cleaned from the wall rather than painted onto the wall. It is very impressive the way the texture of the wall works with this art.
The pieces were done by Paul Curtis aka “Moose”, here is an article about him also on inhabitat.com that goes into his reverse graffitti. This particular piece was comissioned by Greenworks, which is actually a subsidiary of Clorox. I think this is a brilliant advertising idea on their part.
I think the art is very tasteful and a vast improvement over the dirty wall. I wonder though how and if they paid somone for use of the wall? And if not is surgical cleaning against the law? Well anyway please check out the article for more detail and enjoy the images.