Is it possible to use an animated image for the user picture? So I dragged my .gif onto he default globe, and it shows the popup allowing me to edit the dimensions of my image. While I am zooming in/out, it is still animating. I was overjoyed at this, thinking that if the image animates in the edit panel, then it will animate on the login screen.

Nope.

Even if I re-open the image edit dialog, it still shows the animation, but it will not animate no matter what. Is there any way to get this working in the OS, or maybe a program that can do it?
This is currently not possible. You can provide feedback to Apple here:


https://www.apple.com/feedback/macosx.html