I've been thinking of doing this myself, but I have no graphic/artistic talent... so I've been bugging Adam Kinney with absolutely no luck. I'm not sure how many folks are running Win7, but you don't really need to be to contribute to a C9 themepack... creating a desktop image is really all that is needed to start with, then that image (or a set of them) could be combined with a window color into a themepack by someone who does have Win7.

Details on 10 about how to make one for yourself, including a pointer to a set of them done by Mike Swanson (who you've seen on various PDC/MIX videos here on C9): http://on10.net/blogs/sarahintampa/How-to-Make-Your-Own-Theme-Pack-for-Windows-7/