I got a new Pocket PC with Pocket PC 2002 software on it, with that ability to use themes. I got bored one night so I thought I'd make a G35 Coupe Theme.
Take a look:
http://www.pocketpcthemes.com/preview.asp?ID=14004
I would have tried to make an I35 theme, but I couldn't find any really good looking high quality pictures of it.
Time to bust out the cleaning supplies, camera, and find a good backdrop!
BTW - I can make others for people if ya want, just send me the picture you want on it.