Ethan you should try that Cyanogen mod updater.
Click the menu button in CM updater and select Configuration.
Select Rom update settings and highlight the 2 checkboxes
Do the same with the theme update settings and select the checkboxes again.
Select which theme you want to flash and download to your phone.
Once downloaded to your phone you need to rename the filename to update.zip and move it from your downloads folder to the root of your SD card.
Once the file has been moved and re named, you need to reboot your phone into the recovery console (Home and back button).
Once booted into the recovery console you need to perform a Nandroid backup (by doing this before each flash ensures your phone can be recovered from its last best backup)
Once your backup is complete you need to select flash new file and select to flash the update.zip from the sd card.
Once flashed the phone will ask you to restart and after restarting it may take anywhere from 5 to 10 minutes to restart, but you should see a new and different bootscreen to let you know things have changed.
I havent found any more themes to try yet, although there are more on the updaters drop down list im yet to try, but im assuming that to over install another theme on your phone you need to delete the priginal update.zip from your sd card root and rename a new downloaded theme in the same way as you did for the last.
REMEMBER, ALWAYS PERFORM A NANDROID BACKUP TO SAVE GETTING BUMMED BY A BAD FLASH.
As a side note guys, if you find im talking bollocks with any of the above statement then please do tell me to go screw myself