With the higher resolution of the newest expansion, I'd like to see back armor that was more than just a slab of digital fabric. Wings, fur, thorns the list of what back armor could be goes on and on why limit it to something that is so simple. Below I've come up with a list of already in game models that could easily be adapted to equip-able cloaks.
Above are some of my favorite NPC armors that I wish were wearable for my characters. The Sunwell instance has quite a few beautiful character models which should be made into available equipment.
Another NPC with neat back armor.
Even this cloak is so much more than the thin rectangles of digital fabric currently available to players.
Illidan's wings and the Succubus wings would also be easy additions to give player looks a little more spice.
The legendary cloaks from Pandaria are the only ones who come close to being amazing and they aren't transmog-able. So I'd like to see that change. This cloak was so much work to obtain, seems a shame that I can no longer use it.