The Cool Hunter points us to something rather nifty: Diesel--yes, the clothing label--holds a contest to turn a wall on their headquarters into art. There's plenty of examples on Cool Hunter as well as in the gallery.
Check out the Diesel website for more details.
And yes, that's supposed to be the Pope in the picture there. Nice.
Update: Alas, the site is dead. However, just Google Image Search for "Diesel Wall" and you should find plenty of examples.