Umm, why the fixation on Darth, when there's PRINCESS LEIA SLAVE GIRL OUTFIT second from the right bottom row for "Harem Girls???!"
As to which girl could play that role, I'd favor Melissa, although newly enhanced Adrienn might be pretty good for it, if she arrives ... or "Baby" Nicole.
@Dabber: I strongly agree with most of your comments.
All of the costumes could be fun, but it's all about execution. The ones that do badly (I think) are often plastic cheapies (Divine - Supercop, Eufrat - Fast Food, Jenni Gregg - Agent 69) or that have to signal what they are with icons (Divine - Emergency). There's a huge gulf between a lot of the theme costumes we see at VG versus the sorts of costumes pictured at the top of this thread. The VG costumes often are all made of the same fabric and colors, while the better ones that Oquijan posted use a variety of colors, textures, and materials.
When you mix colors and fabrics (the last two snow whites, first ancient warrior, last two pirates), it looks more real than costume. Contrast the last two pirates with the first pirate, and it's pretty obvious. Women put a lot of effort into the way they dress, and I'd rather not have the costumes dictated by some sweatshop in East Asia.