For the Castle room? we could build these out of kleenex and tp or pt rolls to decorate the tops of the shelves. We could also make this a kid competition, collaborating with math and art. Top 5 displayed in the Fair.
DIY - Make a Cardboard Castle from Recyclable Materials: Build an impressive toy castle out of packing tubes, potato chips containers and paper towel rolls! Fun craft for kids who love knights and history.