How do you do this with Avatar/Titles?

[Reno of Shinra]

There's some people inside my board who has custom avatars and custom titels, but it's not because they have X amount of post or been there for a few days. But becasue they were able to kind of "buy" it or earn it

But now hat I want is a way to give them permission to have them select their own avatar or titles, so tehy don't have to go bugging me everytime they want to change it.

Can this be done? using the user group, or making a hack out of it? I tried to look around but I see NO options to give a person rights to have their own custom avatar that they can select or titles that they make up

thanks!