Memory books (called facebooks when a photo is involved) include a page for each retreat participant with their contact information and a space for them to doodle, color, draw, write quotes, thank fellow participants, talk about what a great time they had, or otherwise use however they see fit. They can be full page, half page, or quarter page size. Here are some examples from past YAG retreats:

Full Page:
Full Page Cover:
Half Page:
Quarter Page: