Weeelll, the 6 damage types I've been using are Sharp, Blunt, Energy, Fire, Cold, and Organic.
Sharp is more or less "normal", as practically every weapon is sharp. As for the armor types, you just get to list the strengths/weaknesses of individual units in the caster-upgrade-art tooltip, so you get:
Weak (200% DMG)
Resist (50% DMG)
Immune (0% DMG)
Absorb (-50% DMG)
Status (full duration, half duration, immune)
Not listing a damage type in any of the caagories would indicate a creature takes normal (100% DMG) from the attack.
status is not an attack type but the duration negative effects have. Generally, standard units is full, tough critters with roughly the same stats as the hero take half, and bosses are immune.
I think Elite can be accomplished by just granting the unit in question more HP and higher damage, also heroes are essentially an Elite unit.