A set of 12 monthly images to either laminate or place in an inexpensive frame. You could put it outside your door or near the circ desk if in the library or near the teacher desk or classroom library.
If we want students to read we need to model it! Use a dry erase marker to fill in a title or two to share with your students. If you really wanted to get visual you could print out a small copy of the book image to add to the display.