Trends: Ringback images
This may be the start of something big. After ringback tones, SK Telecom is introducing a way for users to send an image from their cell phone to the phone they are calling. So when your phone is ringing, you would see an image that your caller sent with the ring. Is this the start of a new boom?
From a technical viewpoint this will require quite a bit of bandwidth if it becomes popular. There's also all the issues of spam, and bad people sending vulgar pictures. However if done well it would be a great hit among young people. I'm sure lots of providers will keep an eye on SK Telecom.