Make a mural of book covers and physical books for your reading classroom. Make a mural of book stacks in a library or of book covers from classic books. Either recreate popular covers or simply do solid color jackets with titles and authors of classic books painted on. Open books with illustrated pages can be incorporated into the design of the mural to give it more color and whimsy.
Create a mural full of different characters from classic novels interacting with another. For example, seat protagonist Milo and his companion watchdog Tock of the "Phantom Tollbooth" and at a table with the Mad Hatter, Alice and the March Hare of "Alice's Adventures in Wonderland" or show the Pevensie children of the"Chronicles of Narnia" series playing croquet with the March sisters of "Little Women."
If you'd rather have a mural that is about the people who will occupy the classroom as opposed to the subject they'll be learning about, create a mural depicting people of different ages reading books. Consider the different places people choose to read in outside of a library: relaxing on a bed, curled up in a window nook while rain runs down the panes, or on a fallen log in the woods, for example.
Design a mural consisting of painted windows looking into the different worlds of different books that are appropriate to the age groups that will use the reading classroom. Alternatively, instead of using the windows to look out on individual stories, have them look out on different genres, like fairy tales or westerns. Give each window a drape and shape to match the setting the window looks out on.