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 icone 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 toi mettre en ligne a gif in photo but it's really small it'll just go to icons. Other than that it doesn't really matter. :)
