I've had National Geographic's "Photo of the Day" in my RSS stream for quite a while by now, and I'll never stop being marveled by those shots. Simply stunning photographs. For the past twenty minutes I've looked through many of them, and got hooked on the Big Cats section of photos. Really fantastic creatures. Beautiful and full of grace. I'm fond of the Siberian Tiger (especially the white species). Check out this section with photos of tigers (they're downloadable as wallpapers as well). You'll find all kinds of wallpapers in the wallpaper section too.