I've found some great posters through Chinese Clay Art, also I've picked up wonderful materials from museum gift shops, most of which you can order online. I had a large bulletin board installed and have my students populate it with artists postcards from studio, art show visits and I put some up from NCECA and printouts of work I find on the web, ALSO I use the board to put up an artist of the week for kids to sketch and talk about. There are some great "how tos" and pots shape pages at the end of every pottery making illustrated. I pull out the "how tos" laminate them and have them handy for students who master a skill early and wanyt to move forward solo. They're also good for putting on the wall.
Hope this helps.