why being so unimagineable...take your own photos and resize them to desktop size and you have a real personalized desktop.
Pending on your resolution, 1024x768 or 800x600 (you are not using the 640x480 anymore???), are the sizes you are looking for.
Almost all graphic programs have also tiles with them...called textures, you can use them as well. You can also create your own website, which you do not need to put on the web, you load it as your desktop instead.
There are millions of ideas around, spend some time being creative and you will enjoy the new look even more