How about putting together something like a picture quiz? Get a max of 20 pics of various celebrities of all ages, cut them out and stick them on a sheet of A4, photocopy so each guest has one and they have to identify them. This can work well if all the celebs are famous for the same thing eg film stars, singers, politicians because then you can get people from each decade and it can then spark off conversation, banter and maybe even a few arguments about who was the best movie star of all time etc etc.
Works well if you have some childhood pix of people, or people in unusual poses.