As you may know, gentle reader, I abhor desktop wallpaper. My Windows PC's desktop is set to pure black and my Macs are white ... only because Stevie J, in his infinite wisdom, only provides a small set of solid colours*.
Anyway, back to the subject at hand. If you're into that sort of thing, this site contains a number of nice wallpapers, including the one displayed here, which would be my choice, if I wasn't such a purist.
*Actually, I just had an epiphany! I've taken a screenshot of my black Windows desktop, resized it to fit my Air and turned it into a JPEG with maximum compression, so it consumes almost no space. I have no idea why I didn't think of that a couple of years ago, when I got my first Mac ... what a silly bunt :-).