Personally, I’m not too much into customizing anything of mine – I have a defualt theme, wallpaper and sound set on my eyePhone ;) and never had the need nor the wish to change it. The same goes for my PC desktop – only recently I chose to replace the default WinXP theme with Wall-E wallpaper. But people actually like to change their wallpapers, some of them change it a few times in a week, or even more frequently.
This site, called iDesign * Pre is a good resource for you wallpaper addicts. It has a large database of wallpapers made to fit to your Palm Pre, which is updated daily, and everything is packed in simple and nice interface, categorized.
Off course, they are all free. So – if you’d like anime, 3D, flowers or just Megan Fox on your Palm Pre wallpaper – give it a try.