"This is the world without Self-Expression" A simple idea. Start with a blank canvas and pay local artists to express themselves with a Sharpie. This also allows for public interaction by handing out free Sharpies and letting others express their thoughts too. Plus you get a free Sharpie :)
"One-of-a-Kind" posters with local artists from different cities. Auction these posters off to celebrities and donate the money to a good cause.
An online-gallery of the participating artists and the celebrities that bought the posters and which charities they donated to.