Think about what your book is about. Get a poster and print out pictures that have to do with the book you read. For example, if you read beauty and the beast, you can print pictures of Belle, the Beast, the little characters in it, books (to symbolize Belle’s personality), a picture of a factory to symbolize Belle’s fathers interests (inventing). Just get a lot of pictures and jam them all into a poster with some glue. It’s better if you don’t leave gaps in between the pictures and it would be a lot nicer if the entire poster is filled without a lot of empty spaces of poster!
Good luck! Hope this was helpful! ;)