This feature would be very useful for SIP doorbells.

If someone pushes the button on the doorbell, Sipdroid could show the camera image (or maybe optional, an RTSP video stream) as the contact person's icon before the call is answered.

Like we discuss here: http://superuser.com/questions/679313/android-sip-voip-with-doorbell-view-video-before-answering?noredirect=1#comment861552_679313 SIP protocol already seems to offer a header option for it, but this is not used in any Android SIP client at the moment...

Anyway, it would also be a great alternative if you could set a static HTTP image link to be displayed in the client on an incoming call.