Jealous? XD JK.
I found it in a comment on DeviantArt, but I don't know where he got it. If you find a moving one, you right-click it and it will show the image info. Copy and paste that where you put your avatar.
It may do what happen to me and just say "Invalid File". If that does happen, do this.
Right-click on the image again, but this time click "Save As" and then save it onto your computer. Then, go back to where you put in your avatar and click the "Browse" thing. Then select the image you saved onto your computer, and presto, you got it.