There are currently 8 new pets (with a model of a Hearthstone pet, datamined by Wowhead, that's yet to be added to the Pet Journal). Not much information is provided on the new pets, but here's what's available so far.
Note: Everything is still a WIP and is subject to change.
The Whelplings are listed as "PH", and the model of the Frost and Unholy ones are the same (Unholy Whelpling not pictured). I suspect that their models aren't complete yet, so keep in mind that these images/details may not represent the final product.
Blood Whelpling - unique "PH"
Cavern Moccasin - Drop: Damp Pet Supplies
Crackers - Order Hall: Hall of Shadows (rogue)
Everliving Spore - Drop: Damp Pet Supplies
Frost Whelpling - unique "PH"
Scraps - ???
(NOT PICTURED - currently uses same model as Frost Whelpling)
Unholy Whelpling - unique "PH"
Young Venomfang - Drop: Damp Pet Supplies
From what I can tell, there seems to be 4 new class pets (3 DK and 1 rogue), a new pet reward bag that drops 3 pets, and then Scraps... which doesn't have a tooltip description in the Pet Journal yet. This could mean it's either not yet finished, or it's not actually collectible (I'd REALLY love for it to be though!).
The new pet reward bag, Damp Pet Supplies is from the "challenge mode" version of the new Pet Battle Dungeon. More details in my blog post on this new feature.
Other new pet additions to 7.2:
- Pet Battle Dungeon (see my blog post dedicated to the Pet Battle Dungeon)
- @Mononic1 on Twitter discovered what appears to be a new Trainer on the Broken Isles, Sissix (can't interact with the NPC yet?)
Anyway, more to come, I'm sure. Exciting stuff! :D