The Verge recently published a great article about the golden age of Arcades. Besides being a deep look into a fascinating piece of pop culture history (also interesting from a business standpoint; adjusted for inflation it was probably bigger than today's video game industry, and that in turn is doing more revenue than Hollywood) it is a lovely bit of web design; most striking are the images used as a backdrop for quotes (starting about 1/5 of the way down, with the picture and quote about Mayor LaGuardia taking out a poor Pinball machine.) These aren't normal background; instead, as the user scrolls, the quote section feels like a peephole taking in one part of a larger image, but with the text continuing the move on up.
Here's a version of it in action:
It turns out this is a pretty easy bit of CSS, and has been around for a while. The secret sauce is
The Verge page uses some other tricks, the background-position is center center and the background-size is cover, which means the "image behind" will always be taking up the full browser size -- so obviously there are some extra things you have to think about the viewport relative to the page, but at its heart it's dead simple and has good browser coverage.
(The background-size:cover bit can be used as a simpler form of the stretchy background trick I described previously, but you may have gaps at certain browser size ratios.)