If TouchFLO 3D or whatever other user interface overlay on top of Windows Mobile that came pre-built on your device isn't good enough for you still, you may want to check out French site Actualite Mobile for some SPB Mobile Shell skins or themes.
According to WMExperts, which first spotted the themes, the themes are compatible with SPB Mobile Shell 2.x. SPB Software House announced version 3 of Mobile Shell at Mobile World Congress earlier this year, but that hasn't been released yet.
To view the English translation (via Google) of the Actualite Mobile site, you can click on. Enjoy!
Update: Video courtesy of pocketnow.com reader rafalplus03 .