Fall of the Hyperion by Marcin Jakubowski may well be the single greatest steampunk composition I've ever seen. This image, which comes from the CG Gallery was created for the "Steampunk: Myths and Legend" competition at CGTalk.
He writes that, "In the original myth Zeus and other gods started to fight with the Titans (elder gods) for a right of ruling the world. In my steam version of the story there is a group of rebels inside the country that starts a revolution against the old system. In that system everything is absurdly huge, overwhelming and truly difficult to live in. I want to depict a moment of defeating one of the Titans - the giant robot sentinels that are spectacular signs of power and possibilities of the old system. Beneath people trying to leave the rebel city are frightened witnesses of the great collapse."
Make sure to visit Marcin Jakubowski's website, BalloonTree. Also, if you're a CG Gallery user, go add this to your favorites.