Assuming you mean “something new”, that’s tough given that WoW is kind of what people refer to as a “kitchen sink” setting. (i.e. It has everything but the kitchen sink)
That said, I’d like different types of playable undead, if that counts. Ghosts who haunt their clothing/armor, straight-up skeletons, etc.
Ethereals would be perfect.
I’ll take San’layn Thread for 500, Alex.
The night fae are awesome but can’t help but feel it would be really hard to swing the story to make them leave the after life to fight in wars that ultimately lead everyone back to the afterlife.
https://i.imgur.com/Mp5Wfbx.png
https://i.redd.it/2n3crbhuk3331.jpg
I’d play one
Aw thanks, I was actually gonna say points to the San’layn thread 
Otherwise…
Playable dragons 
Races already existing in lore can be okay.
But yeah the idea was be creative.
Tree people.
Sloths.
Circus clowns.
Easy. Lalafell. Done.
Also Au Ra.
I had to google them and my first thought was loli.
Please say its not.
Half elves or realistic-looking humans.
Male model would be blood elf model, but with normal ears lol
Female would be uh idk maybe the same model as normal wow humans…
I want Drakonids that have the ability to shapeshift into their mortal forms (like how Worgen have the Two Forms spell).
Alliance will shapeshift into half-elves that look like Kalecgos and Horde will shapeshift into Blood Elf looking ones like Alexstrasza. Except you’ll be able to pick your dragonflight to customize your skin color and other physical features like horns.
You’ll always be in Drakonid form in combat and have to manually switch to your mortal form out of combat. The point is more to bring a playable lizard/dragon (think Divinity Original Sin 2) than a new elf though, those are more for the lore-friendly roleplaying aspect and how we see dragons represented in-game.
What? Then Gnomes are loli’s too. People in the FFXIV community literally call them potatoes because of their proportions.
They came in a flood out of the Maelstom. A plague to all.
Skeletons
Of every shape and size. Fast highly mobile!
Reputation All - Hated no gain possible
Weapons - Their own body parts.
Inventory - none! They absord all magic into their being raising IL with each better piece absorbed.
No quests -Exp for killing adjusted up
Skills - a variety of thrown and melee skills
The Dead Rise - You can’t kill what’s dead! They crumble into a pile of bones and reform. While reforming they cause anything that comes within 40 yards to cower until reformed.
I Died Here - Set a hearthstone point anywhere. Use again to recall (The Dead Walk).
Friend not Foe- Other skeletons within 500 yards you can pick one and travel through The Dead Walk gate to them.
A Dead Hand - Summon another skeleton to you from anywhere.
Embrace Life - Open a menu selecting abilities from a list equivalent to what normal play would have. List is populated from absorbed amor.
Travel - Travel form none. Speed increase automatic including flight. No pathfinder.
PvP - Toggle off/on. Default on at logon.
Communication - Skeletons can only hear their own.
The Dead Walk - Beams shoot out from the eyes and mouth opening the gate. The gate sucks the skeleton in starting with the bones of the feet moving up. Exit the gate reforming from the feet up.
I’m gonna go with a new neutral race: Murlocs
After spending years among them, King Mrgl-Mrgl has managed to gather together a group of Murlocs who are less ferocious than most and somewhat enlightened, who wish to join us in defending Azeroth. However, when the question of which faction to join comes up they erupt into a vicious civil war that ultimately results in the red, orange, and yellow Murlocs joining the Horde while the blue, green, and purple Murlocs join the Alliance.
Classes:
Warrior
Hunter
Shaman
Death Knight
Demon Hunter maybe? (some Legion WQs featured Murloc Demon Hunter enemies)
Possibly Paladin and Priest? (would require some lore explanation though)
Gnomes have chests and something resembling hips. Lalafells literally cannot have any proportions more generous than “washboard”.
Bloodborne elves for the horde
They’re shaped like gourds…
They don’t have a human anatomy in the first place with which to have anything OTHER than a “washboard.”
If Night Elves are Alliance, but Nightborne are Horde, then wouldn’t Bloodborne be Alliance since Blood Elves are Horde? 
No wait, that sounds terrible.