Question - Will the costumes come from the caskets or will they be delivered in mail and caskets will contain random consumables?
In my opinion the " rare " items should be receiving instantly, players shouldn't be able to trade them or sell them, with guild mates it would be ok, but with other people, no.
If these costumes would just be sold to rich people with a guild that doesn't even work for gp, probably a guild where it's just that person, or maybe even no guilds then these rare items would lose their uniqueness.
And about the rewards, I think it would be better if there was like 3 or more costumes and we would have to select 1 we would want, maybe make it like when you turn in a quest - it shows 3 rewards and you must select 1.
Most importantly there should be female versions.
Atleast consider the female versions, it's unfair that most costumes are designed for males, there should be 2 versions atleast or provide 3 costumes and we must choose one, one could be male, one could be female and the other could be unisex.