I've added a couple new Wallpapers to my site... but not for computers. I've added a couple for cell phones. Specifically the famed iPhone Clown Fish wallpaper. I considered it a travesty that all of the commercials showed that wallpaper on the iPhone but it wasn't included with the device.
So I've made my own (though there are plenty floating around the internets). I've made one for the iPhone (320 x 480) and also my BlackBerry Storm (360 x 480). Seems to look OK on there and I actually get to see it once in a while - as opposed to only when I unlock or something.
So here's what I have so far... and if you'd like to use one for your device, I'd suggest opening the full size image and saving it to your computer. Then just email it to yourself at whatever email you receive on your phone. Then you should be able to save it as a wallpaper from there.