Honestly, no, I wouldn't ask for something like that. There are a limited number of things that people are permitted to take from hotel/cruise rooms as free souvenirs. Basically, anything "consumable" that is designed to be used up by the guest and not reused by the next guest, so in general, the chocolates left on the bed each night, room service breakfast menus and other stationary/postcards/pens in the drawer, and any individually wrapped soaps/body lotions etc. (although on the latter they are not really available any more as more and more hotels and cruise lines including disney have been moving toward large reusable dispensers). Items that stay behind are those that can be reused by future guests like towels, drink glasses, closet hangers etc. For do not disturb signs, I can see how it might be seen as a kind of stationary, but on balance I think those are meant to be reused and I doubt disney has a big enough surplus stock to easily replenish them.