My school has a partnership with Jo-Ann Fabric and Crafts where they donate unsold inventory to us from time to time. We happened to get a stack of mirrors a couple of years ago. Of course, these ended up in my art room. Some kids and parents helped me paint monkeys in the jungle on some of those mirrors. I believe we ended up auctioning those off at one of our fundraisers.
We also painted these guitars. I drew the guitars on them with a black permanent marker. The students painted them. We used outdoor acrylic paint. It was paint leftover from an outdoor mural we'd painted on a cinderblock wall. We left the circles in the background open (without paint) for the mirror to show. These are hanging in our fourth and fifth grade hallways. They look pretty cute!