For completing collections it would be nice to have a permanent boost to your character for each one showing under your portrait.
Bonecrusher... Furious would give +5 damage Savage +5 damage Wild +10 damage Insane +15 damage.
Gladiator... Shield Riser +20 health Tamer +20 health Caster +40 health Bone +40 health Spear +50 health. I think you get the picture. The idea being you get something more than bragging rights for spending the time and effort to complete these collections.