I went back in to the archives and pulled up some of the advice for when this came up last year: Lots of good advice here from lots of people the original post very similar to the title of this one if you want to see who said what or if there is something I missed reposting.

#1 rule: Do not, I repeat, do not, bring anything (costumes, etc.) that you would be heartbroken to lose. And by lose, I mean ruined. If you can't bear the thought of it, leave it home, because there is always a chance that it won't come home the same and you wan't be able to care for it or fix it.

That said:
Last year I brought 95% of my costumes. most of mine I've made myself and wasn't at all worried about. Don't bring anything that will MOOP: no loose sequins, glitter, feathers, anything that will fall off and leave trash.
I brought most of my stuff becuase I thought there might be other people who wanted to borrow it; I'll probably bring less this year.
I can't advise on hair since I don't have any. :)
We had a really good list of footwear suggestions on our old list, let me see if I can find it and copy it over, I think it's worth repeating.

your fancier stuff (coin bras, belts, etc) should at worst get a clinging layer of dust. Admittedly, the dust is corrosive and you'll want to wipe down the metal parts with simple green and hand wash things like tassels...

The only costume I didn't take was the one cabaret belt that I owned at the time. Not that it's worth a lot of money, but I'm really rather fond of it and I didn't want to take a change with it getting all dusty and me not being able to figure out how to clean it. Not to mention I don't know what I'd do if one of the bead fringes broke out there and left little tiny beads everywhere...
I didn't have a problem with anything else I took. Some things you just wash as usual when you get back (cholis, skirts, pants, etc.). My black tribal skirt was solid grey with dust when I brought it back, but I just threw it in the gentle cycle and it was fine. Some of my tassel belts I smoked out to clean them. I haven't had any problem with the tassels nor have I heard about anyone who has.
I personally don't assign a lot of value to most of my stuff, so if something happened to it, I'd be sad but not devastated. I know other people are differnt, that's why I give the disclaimer about if it's worth that much to you, leave it at home. To me, I'd rather get use out of it than have it sit in my closet and be afraid to wear it anywhere. :)
Some people make stuff specifically for BM, it's really a personal thing.

Last year I took an older skirt that i had and all of my harem pants.. I also took an older tribal bra and belt set that I have but did not take my hard to clean newer set. I also took most of my jewelery.. and all of my turbans. Your tassels should be fine, unless: it rains and mud splashes up, or they are too long and they drag in the wet mud.. For the most part anything that can get wet you can get playa out of with enough washings.. Playa can be hard on metal.. necklace from last year never did recover.. but that is okay it hurts me anyway. I would not wear any skirts that have felt or material on the the trim that dust will be hard to get out of..

Cleaning:

Last year I took a workshop (with Ivy :)) from Gwen Heckroth of Flying skirts and her suggestion for cleaning skirts was to put them in your bathroom.. Seal up your bathroom as much as possible and light 3-4 incense stick and the smoke from the incense will clense your skirts, cholis, harem pants and other stuff.. but how realistic that is for playa I dont know... one suggestion though would be put your belly dancing stuff in ziplock baggies and only take them out when needed. Hand wash the trims to your skirts and spot wash the skirt its self if needed. Be carful of putting your skirts in the wash.. I put one of my skirts in the was and it ripped apart my trim :( (it was my first skirt so I was heart broken..) but luckily got it fixed but then it was too short for me...

Nola here chiming in on a few things...
-Have FUN with your costuming for BM.
-Rememebr that it's REALLY hot. Don't plan on wearing metal next to your skin. (Thanks to Ivy for that tip last year)
-Simple Green is the best for washing out playa dust. I use it on everything.
-My long fringe skirt/belt didn't handle playa too well. Had to wash it and it lost all its shine.
-I put EVERYTHING in Zip-lock bags. Helps keep stuff clean and helps keep the clutter down so you can find it in the piles of stuff that form as the week goes on. I wash the bigger bags out and pack them away with BM stuff.

Just remember...everything, I mean, EVERYTHING will get dusted.
Even in zip-lock bags. Unless you don't open them up, that is.
Bring stuff that's easily washable/cleanable upon your return to the default world. You can still look snazzy in low maintanance costumes.