This mod add Mob Heads for every mob in the game (currently missing some for Villager Zombies).
All the heads can be obtained by killing the mob with a Charged Creeper or as a Rare drop while killing them yourself. (Mobs spawned from mob spawners will drop an head only when killed by a Charged Creeper, configurable)
All the mob heads are coded as DataPack so anyone can add more / edit existing ones.
All the villagers drop the Plains head, so a Taiga Armorer will still drop Plains Armorer head, this is due begin too may variants.
Also horses drop their head based off their color and not their pattern.
Here's all the mob heads in the Creative Tab. The Creative Tab crashed server so I had to remove it and added a command /getheads to get all the heads.
All the heads have been obtained from minecraft-heads.com