Creative wedding guest book

I have been to a few weddings the past couple of months that had extremely creative styles of wedding guest book types. One had polaroid photos taken with a message to be written on it by the guests (with the guests' photos) and one had the wedding guest book write their names and messages on pieces of paper and then these get hung on a wedding tree. I have a few other ideas in my head in case I would renew our wedding vows - perhaps I should take note of all these for that day! Or maybe I should come up with a list and make a blog entry about this!