This post was published more than a few years ago (on 2008-01-22) and may contain inaccurate technical information, outmoded thoughts, or cringe takes. Proceed at your own risk.
Chris Breen, Macworld writer and The Bouffant of Knowledge, as referred to by The Macalope.
The desktop pic is sized to fit up to the 30" Apple Cinema HD Display. On all other displays, simply select "Fill Screen" in the Desktop preference pane, and it will scale to fit.