Every game has concept art. Most games, though, you probably don't care if you see it or not. Then again, not every game is as anticipated as Uncharted 2.
Developers Naughty Dog have released some of the game's concept art to IGN, which aside from being quite nice to look at on its own own, also showcases some of the game's environments.
While company president Evan Wells says they're "not quite ready to give away the details on what you see here yet", that won't stop you poring over the art anyways.