Revenge's idea is pretty good. I think the ability to have them after using a referral system is super legit. Or maybe we can have a community goal. Something along the lines of if we recruit and advertise X amount of people to join and play regularly, then we should get a reward. Maybe something like a party-hat drop party? I think the key is to make them trade-able though. Thoughts?
I just want it clear that driving up the player base is the clear goal here.