SilverWook said:

As Carrie has said the metal bikini was George's idea, what else came straight out of his twisted mind? ;)

It's talked about in this recent interview with Rinzler on his new book:

http://www.fandango.com/movieblog/interview-celebrating-30-years-of-return-of-jedi-with-lucasfilm-insider-742402.html

“In a way Marquand should get the lion's share credit for that, because it was his idea. I think he saw [Carrie Fisher] in Empire and thought ‘Boy, they're not really showing her figure at all,’ and sort of went the opposite extreme. [The concept artists and costume designers] were inspired by Frank Frazetta art and came up with this amazing slave girl costume, which hit a chord.”