The mural is situated in Los Angeles and was created by the mysterious Mr. Brainwash. (For the people unfamiliar with Rosa Parks, Ms. Parks was a woman who, on December 1st 1955, refused to give up her bus seat to another person when she was ordered to do so. This action got a ball rolling that resulted in black and white persons being declared equal in the eyes of the law. She was remembered here at SuperForest last week.)
As a result of Park's action Martin Luther King could speak up, and because King spoke Obama got the possibility to be accepted as presidential candidate. That's the basic thing the mural is implying, it's a chain reaction actually.
If you've spotted your own, local piece of Obama Art we would of course love to know.