Graphic Designers have aways migrated towards the Mac. It should be no surprise then, that there are some really great Apple themed wallpapers on the popular graphic design site DeviantArt.com. These are 5 of my favorites, but you can find even more at the site.
Apple Wallpaper by ~flashrevolution on deviantART
Retro Apple by `-kol on deviantART
love.your.mac by ~Scazza on deviantART
Apple in the sky by ~FT69 on deviantART
MAC OS by ~007TINAR on deviantART