Nothing beats a nice custom touch to your newly minted Ubuntu installation. Many times a nicely done piece of wallpaper or icon can really liven up your desktop experience. You can indulge your artistic craving by stopping by the Art Team website at art.ubuntu.com, where you will find plenty of themes, icon sets, and backgrounds.
If you want to get involved in the process, check out the team’s mailing list and the Ubuntu Art Talk forum. You can find lots of great artwork from around the web in the related art sites thread.