When you only have 20 guests a guest book seems like a little much. I shopped around and of course by around I mean on etsy. I have seen the signature frames before and those are nice but I really liked these 
signature platters by Serendipity Crafts. Chris and my mom took a vote and chose this design. I ordered it in Navy. Each plates comes with a special pen and after guests sign you bake it in the oven and then you can actually use it. I am sure I will just hang ours on the wall.