Basically, it's for everything that hasn't yet become an ingame creature. It's not for creatures that exist but aren't tameable yet, although I won't bite you happen to use it for that, ha ha. Just that it isn't the main purpose of this thread.
So, yeah. Anything goes. If it's something you want to see, mention it, be it a family, or a new model to an old family. If you think there's good reason to believe that that will be added in the near future, add your reasons for that. Those are always interesting to read.
Without further ado, I'll present my list:
CentipedeThe Warlords of Draenei artbook did have this concept art of a centipede-like creature, and although it hasn't made it into WoD yet, it's still possible that that will happen in later patches. At least the idea has crossed their mind as viable.
I am also happy to remind them of how cool a giant centipede pet is, and how perfectly it would fit in Tanaan, with its hellish, monstrous jungle vibe. It would also make a great rep mount. Just imagine.
Peacock Mantis Shrimp
Here come the aquatic pets. I swear, I could geek out about the potential the N'Zoth/Azshara/Deep Seas expansion that we are bound to receive sometime soon (hopefully sooner rather than later) has all day, and this creature certainly won't be the last on this list. A giant peacock mantis shrimp that can run on land would be amazing.
Amblypygid (aka Tailless Whip Scorpion)
Of all creatures roaming Earth, I've always thought Tailless Whip Scorpions belonged right there in a sci-fi movie with very little alteration. They look scary, and they look like alien spiders, and I think it wouldn't be strange to encounter larger versions of them on some planet the Burning Legion might take us in coming expansions. Maybe they make their home in the deserts of Argus?
Octopi/Squids/Kraken
I think that having cephalopods like octopi would be amazing to have as pets. They're known to have a limited ability to walk across land, although it isn't really their favored approach, of course. For WoW octopi, this could be a bit different, and they could be even better adapted to land.
We pretty much have two possible models already, but the only thing they lack is a walking animation/running animation for land travel. If this were ever to become a family, the Ozumat/Kraken/Leviathan model would make a great rarespawn/unique model tame.
Kaiju/Sea monsters/N'Zoth beasts





Now this is the one I can really geek out about for the entirety of the day. Once more, a N'Zoth/Azshara/Deep sea expansion is very likely to happen, and I think this would be a great time to add a new exotic family similar to Spirit Beasts that has this very special "unlike any other" feeling to it.
Because, like Spirit Beasts, it's such a wide category that anything monstrous that could walk on land can fall into it, I think it has a lot of potential. Who doesn't love sea monsters after all? Imagination is the limit. I first thought of this after Pacific Rim, but the recently released game Evolve has fueled that interest even more. This is really something I would like to see happen.
There could be many stories for them. They could simply be deepsea monstrosities lurking down there who naturally developed to be that way. Or they could've grown/mutated due to N'Zoth's influence. Either way, a lot of potential for new, cool stuff, and also a lot of unique rare models.
What do you think? Feel free to add your own ideas!
Note: If the pictures are too large, please inform me so I can change them, or change them. If they are, sorry for that.




