AD&D actually touched on that a little bit when they described the camp and village contents of the various races. Dwarven villages apparently have tamed wolves and brown bears. Wood Elves apparently have giant owls and giant lynxes in their camps. Gnomes train giant badgers and wolverines. Kobolds have boars and giant weasels in their dens. Even Giants got in on the action, with Frost Giants having winter wolves as guards, Cloud Giants having spotted lions as pets, and Hill Giants having dire wolves and giant lizards as guard animals.
This kind of thing really helps the races be more than just humans in face paint. When Dwarves have brown bears as pets, they aren't just Jews or Vikings or even Jewish Vikings - they are a fantasy culture that keeps fuck brown bears as pets. In the original writeup, Gnolls were a crossbreed of Gnome and Troll (don't think about it too much), but once they got hyenas as pets they ended up turning into the lazy beastmen we know and love today.
From a practical standpoint, it is desirable for races to have mounts and guard animals. But because fantasy adventure gaming is tiered, it is also important for races to have access to magical and flying mounts. The mounted warrior archetype requires level appropriate mounts, and as they go up in tiers they are going to need new mounts. The wolf that a Goblin rides into battle at first level is simply not going to cut the mustard at 6th level. They'll need a worg, and eventually something with wings.
To an extent, this seems like it could easily end up with an over-proliferation of magical riding beasts. And if done in an undisciplined manner, that's exactly what could happen. For example: in 2nd edition AD&D, there were regular Unicorns of course, but in order to produce unicorn flavored riding beasts for various factions there were separate writeups for Brown Unicorns, Red Unicorns, at least two flavors of Black Unicorns, at least two flavors of Gray Unicorns, Tan Unicorns, Spotted Unicorns, Striped Unicorns, and so on and so on. Clearly, that's stupid. Also exceedingly unnecessary. I really wish I was making up any of the Unicorn flavor colors on that list.
There are, I believe, plenty of potential riding beasts such that one doesn't have to delve into ridiculous palette swaps to bring culturally appropriate knights of different races onto the battlefield at different tiers of play. To a first approximation, people can ride giant versions of pretty much anything. Giant Goats are saddle ready in canon, and Kobolds can go to war on giant weasels to their heart's content.
![Image](http://cdn.obsidianportal.com/assets/181651/kobold_on_dire_weasel.jpg)
Kobolds on giant weasels? Why not?
![Image](http://www.fantization.com/images/products/detail/14592.jpg)
You can get miniatures of Gnomes on giant ferrets.
Guard animals at the low end are similarly available. Giant animals can be pretty much arbitrarily giant, so even non-threatening animals like hamsters can be powerful beasts of war.
![Image](http://24.media.tumblr.com/a73d095b936ac61a97d30fc4848a9358/tumblr_mi6mtbkSZx1qzv4gao1_400.jpg)
As this Gnome's giant hamster clearly demonstrates.
The top end is, I will admit, fairly limited. When it comes down to it, you are going to be riding a Dragon. You might be riding an Undead Dragon or a Mechanical Dragon or whatever, but it's going to be your character on a Dragon when it comes time to to joust with the Lich Emperor for the fate of the Time Shards. That's just how it goes. However, that's actually fine, both because there are a lot of dragon flavors to choose from and because most characters don't get that high level in the first place.
Where things get a little fuzzy is when the pool begins to get deep. Obviously you aren't going to be able to fight a Dragon on horseback, because the Dragon fucking flies and breathes a cone of flame that wipes everything as weak as horse off the battlefield as an afterthought. In the mid range, characters will need a couple of mount upgrades, but that's still in the range where characters should logically be getting their mounts from the high end stables of major cities rather than as gifts from gods. This means that there need to be magical mounts and flying mounts that are available for purchase.
If you go through the monster manual, that has apparently always been the case. A Griffon has costed 5,000 gp since before I was born. But it's not enough for such beasts to have a cost, they also have to be somewhere you could buy them. Which means that races need to have domesticated medium and high end riding beasts associated with them. Like how Goblins get their wolves, but then they also get worgs and guulvorgs and shit. Only hopefully not like guulvorgs, because those are slightly embarrassing. Maybe Manticores or something.
Drow: The Drow are pretty easy. They have actually a whole fuck tonne of crazy shit at their disposal and can actually get cut down a bit. I mean, do we really need that thing with all the legs and consonants? They get several flavors of giant spider (including the immensely powerful Phase Spider), and several flavors of evil black horse (Black Unicorns and Nightmares, for example), they are doing fine.
Dwarves: Dwarves are usually not shown mounted at all. That being said, you can get pretty far with Bear Cavalry that they have apparently been kicking around since before I was even born. Thematically, they seem like they would be drawn to wide and stable mounts like Basilisks in blinder helmets or Giant Spiders. Duergar, of course, are known to ride giant tarantulas into battle, and it seems like there's nothing stopping other flavors of Dwarves from doing similarly. Sooner or later they are going to need something that gets them off the ground though.
Halflings: The basic Riding Dog goes obsolete pretty fast, but there's a lot of life in Blink Dogs and Giant Eagles. They'd like something tougher, but they have mobility nicely handled.
Gnomes: With their innate ability to talk to burrowing mammals, and the effectively limitless size of burrowing mammals in D&D-worlds, Gnomes have a pretty sweet selection of giant animals for use as beasts of burden, guards, and mounts. But while Giant Space Hamsters are admirably tough, they're ultimately going to need something with mobility powers. I don't know. Flying badgers or some fucking thing.
On the flip side, there are a lot of monsters that would make good mounts but simply aren't assigned anywhere that you could plausibly get them in-game to use as such. There are places to get Giant Eagles and Giant Owls, but where exactly are you supposed to get Hippogriffs, Griffons, Manticores, Wyverns, Unicorns, Pegasi, Displacer Beasts, Carrion Crawlers, Chimerae, Gorgons, Dinosaurs, or Rocs?
-Username17