before 5u was released, i was hoping that they were linked to the character leaderboards. for example, a fight would become far more intense if suddenly the world's #1 tina popped up in ranked. this way they would actually mean something worthwhile too.
as of now, they just seem to be a personal thing, with the gold "1", silver "2" and bronze "3" crowns representing your primary, secondary and tertiary characters respectively, determined by the amount of cp (character points) they each have. of course you would need to play at least 3 or more different characters in ranked to obtain them.