just wanted to add, I asked my WC if I brought my own Table cloths and napkins would Disney be able to set them up, even for a fee, and she said no, that I would have to designate someone to do it. Not only that, but that whoever I designated to do it, would only be able to access the room an hour before the event!
Pretty much every question I've asked that involves Disney setting up something I bring, the answer is always no. Not sure if this will change when I get a wedding planner. But you definitely want to check with them on that before you make too many plans to bring things. I'm sure they will do the normal things like favors and placecards but they may give you trouble with the centerpieces. You could probably get around that if you had Disney add some floral to it.