You can make your own 'moving display picture' by using your webcam, directly from within Messenger.
You can even make it react on the emoticons you use in a chat. So, for example, when you type
, the display picture will show the small video of you doing a sad face.
The same can be done with 'avatars'. These are called "WeeMees" and/or "Quebles". With WeeMee's you can create your own 'human' looking display picture and color every aspect of the figure (hair, eyes, etc). You can also put many different cloths on it, backgrounds, etc...
Together with this you could of course create your own dynamic picture or a static display picture by drawing things yourself in a graphics program.
All those things can be found in here:
Tools > Change Display Picture...
In that window you'll see a lot of links at the bottom and buttons to create the things described above. To find more premade display pictures you can browse hundreds of sites across the net.
/ 
