I'm very happy to see that class content will continue to be a theme going forward in Legion. One way in which this will be happening is that there will be continuations for the Class Campaigns in 7.2.
While there will be new artifact appearances to unlock (ones that were datamined during the Beta but have been unattainable so far in game - I'm super excited about the Prot Paladin one that gives us a flail) the main reward at the end of the second part of the class campaign will be a class-specific mount.
All these mounts will be capable of flight, which is good news given that 7.2 will also allow us to complete part 2 (of 2) of Broken Isles Pathfinder.
Check out this post from MMO-Champions for the images.
Monks seem to be getting a somewhat Celestial-looking Tiger mount. It comes with spirit beads, a big keg of brew on the back, and some drinking gourds hanging on the side. I don't know if it sprouts wings or just mystically floats when flying.
This appears to be a skeletal horse burning with green fel fire. Much as I'm proud of my greed dreadsteed, it's still using a vanilla model, so this is a pretty big update. The horse is mostly covered in what looks like black barding, and it has two big horns, but underneath the armor, it is glowing bright green.
The Hunter mount appears to be some kind of winged wolf. The wolf has wooden armor with fang-like spikes on it and its forearms have feathers.
Mages have some kind of magical floating disk, which they can surf on like the Red Flying Cloud. It seems to have an intricate design with orbs of arcane energy at three points around the disk.
Warriors have what looks like a red dragon with spiky metal armor on it. I can't tell if this is a super-updated Proto-drake (it appears to have only four limbs, unlike most dragon-dragons who have six) or if it's a Storm Drake (though it doesn't have their glow.) Anyway, big red dragon-like thing.
Paladins get a much more modern-looking charger - a horse with glowing golden eyes and white barding with gold and blue accents. Naturally, the Paladin mount comes with a big libram hanging from the saddle.
Priests get a... ok, imagine a gryphon, but instead of an eagle head, it's an owl (think like a barn owl.) The Priest mount seems to radiate light and bright feathers and has a big glowing symbol on the back (I'd love to see if this changes when you're Shadow-specced, though I doubt it would.)
Rogues get a giant raven, which has a little bit of armor on its wings and head, and seems to carry a cloud of shadow around with it. I'm very happy about this one.
Shamans get a big air elemental. They ride on its shoulders, and the elemental has big purple bracers (with gold and lightning-blue accents) as well as a metal helmet and harness. Like the Mage mount, Shamans will sort of "surf" on the elemental's shoulders. Again, very happy about this one.
This appears to be a shapeshift - a kind of alternate flight form. You'll take on the form of a massive horned owl with a moon symbol between the horns and a little armor on the wings.
Demon Hunters get a big armored Fel Bat mount, who wears a black-and-yellow helmet with a massive blade on top of it. The Fel Bat also bears some Illidari runes on it (presumably to keep it under control.)
Death Knights will get a massive undead fel-drake - a kind of update to the Frostbrood Vanquisher mounts you get for Glory of the Icecrown Raider. The drake glows with fel magic and is pretty much skeletal.