Before mass printing in the 20th century it was common for the endpapers of books to have paper marbling. Sometimes the endpapers are used for maps or other relevant information. They are the traditional place to put bookplates, or an owner's inscription.
As of 2010 there are many styles of endsheets or endpapers that are specifically designed for use with different bindings. Read more on the history of endpapers.
above image: stylish endpaper design using logo graphics which represent characters in the story; endpaper of a book printed by bigger dot for zova books.