for the custom maps.
let players give users a rating based on all of his/her maps
It would just be easier to generate an overall creator-score, based on his individual maps scores... add them together, divide by map count, and bingo... overall Creator-score.
No need for another voting-system, when ppl allready give the creator votes.
I think a rating, however it's calculated (I've seen several discussions on this subject) should be by map and not by author. A rather bad map maker can have one good map and a very good map maker can have a bad idea (or day). I'm playing the map, not the creator. Besides that you don't want it to get too personal I guess. Unless what you're asking for is a ranking system like the high score tables, but this time for map making. I hope we don't have to make a competition out of everything....
human nature WILL make a competition outta it