At first I thought it was pretty pointless, but I signed the petition because I think that the one they chose sucks, and the animal ones not only look great, they are also unique. We all know the waves, skies and landscapes from windows or Mac OS. But the animal thing is new. And I love the way he did it. They are usable default wallpapers since they are not distracting, and they are easy on the eyes (I could never use a picture or geometrical figures as wallpaper, it drives me crazy. Maybe I got some kind of ADD.)
Oh, yes... why this is important:
If you look for linux on google or google-video, you will inevitably get screenshots and compiz videos. Most of them on Ubuntu. Whatever is the default wallpaper will be there on video tutorials, on presentations, in magazines.
When I first used Ubuntu I was pissed off that they hid the boot log. I couldn't understand why they did it... But when I see the reaction of people watching my computer boot up without bootsplash, I totally understand it, and I think it was a vital idea. The first impression is very important.
Discussion on Ubuntuforums
On second thought I'm not THAT sold on the animal things... But the one they want to use now is a step back from the Feisty default theme, which is an excellent default wallpaper IMHO.
I like the idea of the anymal skins very much, but I don't think the ones in the link above are optimal (just tried them as desktop backgound).