This is tricky. Because DWs are non-traditional, I don't really think there is a set etiquette guide. The Knot says that you should pay for any attendant accomodations if they have to travel, no matter where they come from.
This was so not realistic for us and we only have 6.
Instead, we are giving them all a "credit", which basically covers the deposits or airfare. It is between $250 and $500 per person, depending on their financial situation.
I've done little things like purchase the guy's shirts for them, signed up for coupons at Men's Warehouse where they will get thier suits. I had to buy the dress for one BM who is having tough times right now.