Probably not alot, given how much fun you can have with mods. There are a few, tho. Thing is, to even notice the lack of caste graphics, you need mods.
More support for castes, in general, would be nice. I'd like to be able to make a caste of males who do not impregnate women (sterile men). You can fake sterile women, but worldgen doesn't take this into account and gives them babies anyways, or so it seems. They would be a low segment of the population, but they would deffinitely help keep down the population explosions.
Also, it would be nice to have a caste that works like real-world indian castes did. You can move up or down the ladder under extreme circumstances, but for the most part you are stuck where you were born. And your caste is your parents' caste. And presumably your grandparents' caste as well.
I'd use a more comprehensive caste system to make the "sentient" creature. Elves, Humans, and Dwarves together as one Creature entry. Elf + Elf = Elf. Elf + Human = Half-elf. Half-elf + Elf = Elf, and so on. Dwarves wouldn't get to breed with Elves, but could breed with Humans to create Muls (who are sterile). Maybe that's all wishful thinking, but fantasy literature is rife with humans bearing an ancient touch of the blood of the gods/fairies/dragons/elves, and it would be nice to model this.