Customizing Gnome, part 1

I've started tinkering around Gnome and customizing the look and feel of my Linux box. So much control it makes every control freak look like a baby. There are tons of themes out there for you to choose, and if nothing is of your liking, you can just simply change everything till it becomes perfect. Now I'm looking for a wallpaper to go on my desktop, something that would make people go "dang that's awesome!".