If you browse the desktops that are included with Vista and you find it lacking, there is always the collection from Hamid Darwish to spice up your desktop.
He’s the Flickr photographer that Microsoft hired to do something special for the desktop. These are the Photos that didn’t make it:
You can download the whole collection as a ZIP file from his site. I’d unzip it directly to C:\Windows\Web\Wallpaper\ so it’ll show up when you personalize your desktop.
I’m using this one on my Laptop at the moment: