a recolor of those (well, one of those) Pandaria phoenix mounts.
I don’t think any other mount has that type of model, does it?
I don’t even know what they were from, was it the raid achievement?
I don’t mind if they want to keep those specific colour models unique to that specific achievement, but a recolour or something of that type of mount would be nice.
Everything that was removed ever just to see the incoming tears.
The current setup is fine, but more HD remakes of vanilla stuff would be on point. That and class gear, like the 3 part sets before, except with colour pallets that match recent tier gear so they can be mix and matched e.g able to acquire a few different helm options.
My self-esteem
Original Armani battle bear
Yes. 
Things I would love to see come to the trading post in 2024
Proper long coats like Genn wears.
The Demon Motorcycles that got datamined.
Kilts, Like some proper Celtic Kilt mogs.
Steampunk armor mogs.
Propper chainmail chest pieces or gambesons.
Some knight transmogs that are a bit more practical, no massive shoulders. Just clean functional looking knight armor.
More color options for the Love Witch set.
High-rez updates for older sets like the Judgement set.
More tattoo themed chest pieces. Or just give us baseline tattoo options for all our races.
That’s all I can think of at the moment.
Might of the grizzlemaw
Reins of the Mighty Caravan Brutosaur
Frostmourne mog/thread 
Cloudsong glaive
Heh, you know what should be the next 12 months completion reward?
The unused MoP Challenge mode set colors.
Hear me out.
The un-used old classic warglaive model all the old dh’s used to use in tbc. I can’t find them on wowhead but yall know what I mean
Simple miniskirts with no hearts.
Multiple colors of:
The mailkinis that were datamined like a year ago
Overcoats like what Genn Greymane wears
The shields the Silvermoon City Guardians carry
I’d love to see some chest mogs that have a cloth drape diagonally to match the new shawls. Right now the physics are neat, but there aren’t any good chest pieces to give you a cohesive look with them. Make it look more like a wrapping a cross the armor.
Wouldn’t mind seeing some decent shields, larger but low fantasy in appearance. Sometimes I don’t want a fire spewing dragon head but I also don’t want a buckler.
Hats WITH long hair.
Please Blizzard, I would literally be more excited about this than anything in The War Within.
Still don’t know how we’ll obtain it but I hope we get the Dark Ranger General’s Kit transmog set aka Sylvanas armor. 
Mage Tower Artifact weapon recolors.
WoD challenge mode weapon recolors.
You know, the things I’m not allowed to have since I didn’t play the game at the exact right moments in time.
The Black and Red Plate Boots that are currently locked as level 60 honor rewards that are Paladin only that require 1800 rating to transmog.
I’m tired of this model being locked behind class and pvp nonsense.
Black Qiraji Battle Tank.
Updated Katana model would be super popular. Same with samurai armor.
Bring back the Alliance and Horde specific choppers.