The other weekend we spotted this cardboard honeycomb Wish Wall by Cardboard Design in the window of Paper Presentation (which shares the same owner). We immediately thought of what a cool thing this would be in lieu of a wedding guest book! Guests write their messages on slips of colorful paper...
The effect of the colors is pretty cool, and you can also write letters (like "Guest Book"), lite-brite style!
It comes in this small ready-made size, as well as in custom sizes.
Photos above from here, bottom photo by us.