I don't understand what you want to buy ? what do you mean by "animated avatars" , they should be gifs ? can't you simply buy an account with PNG or JPG and simply put a gif into them ?
Old account (i.e ~2-3 years old ) were allowed .gif avatars.But now it is not allowed not any member rank but still some old accounts have their .gif avatar as their account avatar and is pretty in demand as now it is not allowed and user find .gif avatars more attractive so it does make sense.If you try to put up a .gif avatar it will refuse up and ask you to put up a .png or .jpeg or any non-animated avatar
