Morgan,
You may be interested in using
Masterpiece Cards, a set of 250 art history flash cards of famous paintings. Each painting is reproduced on a 4" x 6" Card; on its reverse is an art analysis of the work by an art historian, as well as the vital facts about the famous painting.
The set covers the Renaissance to the 1960s. If any themes or images are too mature, it's easy to remove the objectionable content (and not so easy with a book!).
Your readers might also be interested in the (free) blog about famous paintings, too. You can see samples and sign up for the blog at
www.TheMasterpieceCards.com.
Susan Benford
Masterpiece Cards