Love this idea! I Spy Wedding Camera Game~ give each guest a disposable camera and make them go on a photo scavenger hunt for each of the items on this poster that is displayed. Then have them turn their cameras in before they leave!
Want a guest book you'll actually look at again? Create a photo book of your engagement photos for guests to sign. This is the best alternative guest book idea I have seen. maybe to go along with a traditional guest book?