I remember seeing that image way back in the QJ days and seem to recall someone saying they were from a PSP related advert/game?
Here is a very nice subtle wallpaper that I have been looking for for months! It's hard to find a decent not obtrusive background that's just that; a background. I had a lower resolution one which I've been using, but I think these are the originals.
I attempted to extract them from media center my self but I could only locate small PNGs of the exact same image.
http://blogwindows.wordpress.com/2007/06/05/vista-mediacenter-wallpaper/