Everytime I change mine, I have to wait a few days or so for it to actually work.
Though I haven't gotten an error message or anything.
This is the same with me.
I had to wait a few days to change to the fel cat one.
But now, it's back to normal? I didn't change it.
Yesterday I uploaded a one of the Medic I made in SFM.
the one linked is animated.
Sorry, I just peeked at the imgur page for a second.
Edit: In Opera, I'm fel cat. In Firefox, I'm normal.