I've finished my first pass of Maldraxxus and updated our database! You can see the current list of which looks are and aren't tameable in our guide:
https://www.wow-petopia.com/shadowlandslooks.php
Just a quick breakdown:
Skullboars:
4 of 6 looks are already tameable. 1 is untameable but should be available by launch. 1 (green) hasn't been found in the game yet.
Death Chimaeras:
There are 12 looks total (6 colours, with or without horns). 4 currently tameable. 1-2 more could possibly be made tameable. The rest haven't been seen, or are on mobs that can't be made tameable
Stitched Darkhounds:
Just 1 of the 4 new colours (green) is currently tameable

At least 1 more (dark) should hopefully be tameable by launch. 1 other is only found on a mob that is friendly, and 1 more (teal) I haven't found in the game yet.
Death Rocs:
Sadly, none are yet tameable.
3 of 4 colours appear on mobs in Maldraxxus and should hopefully be tameable by launch. The remaining colour (green) appears on a dungeon NPC, which means it may or may not ever be tameable.
Tauralus:
Sadly none are yet tameable, and only 2 of 5 looks seem to be in the game so far. At least those 2 should hopefully be tameable by launch. Maybe I've missed others..
Mana rays:
3 of 4 new mana ray colours are already tameable, and the last should be by launch. Note there are also two old Draenor skins that still aren't available in the game.
Helhounds:
There are 8 looks (4 colours, chained and unchained). Currently 3 (all unchained) are tameable (as hydras, which I think this is silly). At least 3 more could be tameable by launch, w/ chained brown on a once-off mob. Chained black is only found on friendlies
Spiders:
4 of the 8 new-model looks are already tameable. 2 more (in Revendreth) should be tameable by launch. The remaining 2 (red and dark green) haven't been seen in the game yet.