Just have horses, fastest mounts should have plating to "stand" out.

Honestly every single thing on the list in some form or another could be adopted into TES by melding it with unknown critters we have not seen in TES as of yet. We have never been to Black Marsh, Valenwood or mainland Morrowind(Tribunal doesn't count as t gave us no indication of the fauna there, but that gives us a Durzog mount btw). Having said that. I still said no to almost the entire list because they are terrible and incredibly generic options.

We know that at least TWO breeds of Khajiit can be used as mounts. But I am pretty sure they are only for Khajiit. One weighs like a literal ton(that about 10 Altmer?) supposedly and the other weighs like 3 tons somehow iirc(30 Altmer wasn't it?) though those figures are probably subject to change. These could be huge [censored] battle cats.

Guar are kind of lame mounts imo. At least not for battle use. Cute sure, but not for battle. Alit, Nix Hounds and Kagouti on the other hand...remember, Dunmer don't like horses very much...and that is after centuries of Imperial exposure. Imagine before that...kind of awkward to mount a Silt Strider though isn't it? I just cannot picture them being fast for some reason, then again we never really see them actually move. Flying Bull Netches would be badass though and fits perfectly. So yeah, that covers what the Dunmer and Khajiit?

I guess Mammoths for Nords and Horses for Bretons and Imperials...oh yeah...

I don't see the Bosmer really using mounts. Unless it flew. Thick ass jungle makes Mounts almost useless after all.

Orcs eat horses so...maybe. Mongols ate horse after all and there are not many if any cultures that loved and used the horse more than them. Chaurus maybe?

Redguards could ride those Tremor worm things that were in one of the mobile games I think. Or be lame and use Camels...

Argonians honestly coyld ride pretty much anything considering Black Marsh. I wouldn't mind a Lizard thing like the one from Star Wars Ep. 3 that Obi Wan rode. However they would need to make it fit somehow. Give it some backstory because we honestly need more lore on the Argonians and I care little about who gives it so long as it is good. They could possibly use Wamasu but that doesn't look comfortable and it might be a more 'shocking' experience than they thought.

The Altmer using some kind of Big Ground bird isn't completely out of line imo. They better not call it a sunbird though. Unless that is where it got it's name...