well, I'd certainly like an Undead based Religion, a Draconian based religion, an Earth/Nature based religion, and so on ... I'd like to see limited auxiliary units being used based upon which religion you follow ... and of course for the Undead religion to have hordes of zombies .... heck, it would be cool if you could mod in a Zombie infection mod, start of with 1-3 infection starting points, and play as the Soveriegn in a world undergoing the Zombie appocalypse, just you the person/unit, maybe a small band of up to 10 adventurers ....
It would also be nice to have "angels" in a few religions and "demons" in a few religions. For instance, Fire, Earth, and Death demons, Air, Water, and Life angels. Of course, I would want all to look scary looking with a variety of scales, fur, feathers, and skin. For instance, I imagine an Air angel to be a flying scaly draconian with glowing eyes, shooting electricity out from its feathery wings or somesuch. These would be powerful creatures with a high upkeep that you can only recruit if you are following a certain religion. Also, if you are following the draconian religion (an off-shoot brand, not elemental based) ... you will have a natural "sense" of where all the lizardman kingdoms are, so the location of lizzie caves will be revealed to you on the map, and you can go there with Sovereign/Royal/Hero/Diplomat to recruit them to the cause .... and it makes lizzie and other reptile units have strong morale bonuses in your army. ... There will probably be a questline along the path of the Draconian religion, which will eventually lead to raising your own dragon.
Also, a highlevel spell only unlockable by the Undead religion would be a powerful death spell to contact a powerful Bone Dragon, or Draco-Lich even .... and you would have to recruit him and may a hefty payment ... or something. Maybe recruting such a Draco-lich would require a substantial essense cost (like 5? 10? more?)
Of course, there are all kinds of skelletons, zombies, spectres, and other forms of undead creature that could be used ... especially lots of different kinds of zombies from all those Undead fiction stories out there. And most can be fit into fantasy.
Water-angels would probably either not leave the water, and be as mermaids, or they could be giant amphibians, like the powerful prophets that ruled over the lizard kingdoms in warhammer.
However, I see nothing wrong with having a human-only game ... with most of the army being massive legions of (wo)men. I would however like to potentially unlock powerful auxiliaries based upon Religions and Quests. (also the MasterSword should be part of the MasterQuest ) (in addition to the certainly powerful adventurers/heroes and royalty you will aquire over time)
I would certainly like to see Royalty visibly age after a time, but never truly die. Not sure if this is possible, but it would be neat. Or at least an ability to make my more elder queens, kings, barons, duchesses and so forth ... to look older, from a slight greying of the hair to a total grey-white of the hair and paler skin ... possibly wrinkles too, although depending on how often or close-up we see our royalty, it could be different. For all intents and purposes the Sovereign could very well look exactly the same for the whole game (other than equipment) but yea, deciding not only stats/backstory/skills/weapons/spells, but also starting off with visual customization would be nice. Maybe I want an eye-patch, a couple gold fillings, a war-ponytail, and war-paint. Or maybe I want thick over-sized nerd glasses, a frail physique, and long matty hair. Or maybe I want a really cut and bulky sovereign with war scarring, a missing ear, Either in full armor or in the more free-form barbarian leathers.
Just stuff like that. Obviously some things could be a reflection of stats, but I would rather not get Fable-y .... just to have that option if I wanted.