iPhone: Vodafone, T-Mobile Carriers, and Ringtones?
Besides AT&T and Cingular, there are logo images for T-Mobile and Vodafone in the iPhone's file system.
Both Vodafone and T-Mobile are heavily rumored to be Apple's mobile partners in Europe/Germany. No other carrier's images are included.
Apple appears to be storing Ringtones as unprotected AACs (m4a) in a "Ringtones" directory on the iPhone:
This suggests that adding custom ringtones would be as easy as copying AACs into the appropriate directory. There had been rumors that Apple would be incorporating Ringtone functionality in iTunes for the iPhone.
Additional iPhone tidbits have been posted at MacRumors.com/iphone