Well this is the Elemental Ideas Forum so here's another one of my topics providing ideas for the game.
Every unit can have one or more tags which characterize the unit. These tags can be used to provide the units with benefits or disadvantages for the types of terrain, weather, weapons, spells, etc., :
1) Humans: Probably one of the more common unit types, can be found in almost any location on a map and the most likely to have established towns. One example would be a Crossbow Man.
2)Beasts: I recall reading the game has beast types already and these would more likely be found in jungles and forests yet can be almost anywhere. They are unpredictable yet probably have dangerous reactions to travelers. One example of a beast would be a giant squid.
3)Demons: Might be found in the deepest areas of a dungeon or cave yet sometimes have been summoned with powerful magic. They are a strong unholy force. One example would be a succubus.
4)Animals: These creatures are more likely to be found in areas of vegetation yet are unlikely to attack travelers. Many types of animals can be domesticated then trained to fight and some even made into mountable units. One example of an animal would be a horse.
5)Angelic: Might be found on the top of the highest of mountains or plateaus yet sometimes have been summoned with powerful magic. They are a strong holy force. One example of an angelic would be an Arch_Angel.
6)Undead: The undead are more likely to be found in caves, graveyards or dungeons yet sometimes have been summoned/created using Necromancy magic. One example of an undead would be a vampire.
7)Insects: Insects can be found anywhere on a map except for areas of where its cold. They will thrive in wet warm locations. One example of an insect would a giant spider.
8)Magical: A magical creature is one which has been created from magic or something which has been greatly changed because of magic. One example of a magical creature would be an Iron Golem.
9)Plant_Life: These are usually found near sources of water and thrive in wet warm locations. Plant_Life cannot move on its own and typically used in war for defensive reasons. Sometimes magic can teleport Plant_Life type units into battle and special mechanical moving devices have been used for moving Plant_Life units. One example of a Plant_Life unit would be a Giant Venus FlyTrap.
10)Mechanical: These are found being controlled by another unit type of high intelligence and are usually war machines which cannot move or strike on their own. Only through magic would it be possible for a mechanical unit to move and attack on its own. One example of a mechanical unit would be a catapult.
11)Reptilian: These are usually found in warm/hot locations on a map with a preference near water and stay away from cold locations. One example of a reptilian would be an alligator.
12)Alien: These creatures are rare and not from this realm. They might have come from the stars inside an asteroid or another dimension from a torn astral portal.
Ideally the custom modding of units would allow gamers to create their own special units thus if someone wanted to create a demon spirit they could give it the tag of being undead and a demon. Another unit someone might want to create would be a two-headed fire spitting lizardman which would have the tag of reptilian and magical.