Gifs are meant to be in the fan art section since it's something a fan has edited. The only exception would be if they were icona sized, but in that case they'd be moved there automatically.
Anywhere, photos, fanart, icons. Just depends on the size but it'll automatically do that for you. Like if te carica a gif in foto but it's really small it'll just go to icons. Other than that it doesn't really matter. :)
