We use small spiral bound scrapbooks from Michaels. DS has a 5 x 7 sized book and I bought myself a couple 3 x 3 books. I decorated the cover os his book with stickers, and used letter stickers inside the front cover to write out 'this book belongs to'
I will put a pic of ds and the character in his small book and use the autographs from my book in the scrapbook.
Oh, if you are going to add photos to the album, make sure to leave blank pages next to the page the character signs. Or if you are going to dismantle the book and scrap the pages, make sure only one side is signed.