Several years ago I purchased a wonderful wall calendar from Peaceable Kingdom Press entitled Celebrating Children's Books: A Tribute to 12 Outstanding Children's Book Illustrators. I thought this was the perfect calendar for the classroom and looked for one each new year. Not wanting to part with the whimsical and charming illustrations from some of the best children's literature, I cut apart each old calendar and laminated the pages. Instead of using them for mere decorations, I wanted to engage my students. I wanted them to wonder about new books or be reminded of old favorites. Now, I display these illustrations on the back of my classroom door. I change them periodically and always challenge the kids to "guess the picture book."
Update: Unfortunately, Peaceable Kindom Press no longer publishes these calendars. I'm always looking for other alternatives so leave a comment if you know of one!