When I have to replace a window shade I save the old one for my grandkids visits. Offer them crayons, colored pencils, paints, and let them "go to town" with an artist flair. Happy Picasso.
This page contains the following solutions.
Do you have any old and/or unused white window shades? Let your kids or grandkids draw on them with crayons or paints. They can then be washed with a sponge and mild dish detergent and used over again.