I came accross this idea online, as a non-traditional guestbook. Every guests signs a blank puzzle pice (they come in sets that are universal, you can buy as many sets as you need and the puzzle keeps expanding) see link http://store.adventureworks.org/new.html it's called the 'community puzzle'.
Has anyone tried this? The other option would be going to a carpenter and asking him to make a puzzle with as many pieces as there are guests.
Any suggestions/opinions would be appreciated.