As much as I like the current units, I still think that there can some more added. With the archers, I suggest adding a crossbowman (can only fire in straight path and penetrate first unit and hit the unit directly behind him, not affected by armor bonuses). For the infantry, add a spear-thrower (ranged infantry) or a mace soldier (can stun any unit it attacks for one turn, doesn't stack). The calvary is fine for right now. You could add a catapult for the siege weapons. And in the shop, add an undead horseman to the other undead units. Just some of my ideas, but I really want to have the crossbowman and catapult as there are few archer and siege units.