Here's one I came up with entirely on my own that beautifully brings out the fall colors.

For a more complete experience, The orange wallpaper you see in the background can be downloaded from

http://zone13.digitalgrafis.com/files/intelmac_red_16001024_notxt.jpg

Interestingly enough, I found that wallpaper when Googling "Ubuntu wallpaper" and browsing through Google's own image results.