Yeah, Amy was remembered by pretty much everyone during the final weekend; Star Wars staff, Disney staff and members of the 501st because she carried the shoes around the previous weekends.
The photographer who took the picture of Billy Dee & Amy was only taking pictures of the rare & cool stuff and even then it was only one or two pictures. She pulls out the shoes and he snapped away like mad and took loads of shots.
Absolutely anything can be signed, but you're limited to one item per person, per signing.
Which reminds me, while I was in line for the Ray Park signing and nearing the front, I pulled out the shoes and the print and heard gasps and bitching all around me. It was either people saying "Holy fuck, look at his shoes." or people saying "What the fuck is he doing? You're only allowed one thing signed.". I think the staff were confused also, until I explained that it was only the print I wanted signing.
I'm pretty certain that it's an exclusive deal between Disney World and Lucas, so this will only be happening in Orlando.