This is such a great idea for Matt's PhD Graduation Party in 5 more years! or the kids graduation parties later on. Instead of guest signing the picture at a party. Have everyone one sign a puzzle piece and show who was a piece in your special day.
One of our students was moving before the end of the school year. Each student colored a letter and then I photographed them with their letter. Printed, cut out, and mounted the photos in order for the message. His mom loved the going away memento.