CDs with lables that make them look like old vinyl records . You could also set up an old RECORD PLAYER and have REAL VINYL records for guests to play. Ooooh, perhaps even give the records as Wedding favors?
A unique DIY for your wedding guest book: Create a photo puzzle using your favorite engagement photo and set out the puzzle with pens for guests to sign. You'll have a keepsake that will be pulled out for years to come.