Here are some good sources of photographs and art to enhance your teaching. Some are free and some are for purchase. Be sure to adhere to copyright laws!
Ancient World Mapping Center Maps for Students Digitized maps for educational use. Teachers and students may use these maps for educational or personal use. Most of these maps come with a customizable blank version, quite suitable for quizzes and tests.
Centaur Systems carries the professional quality JPROGS image collections (many 1200 pixels wide) on CD-ROM. Collections available include Romana, Pompeii, Hellenika, Hispania. Rome the Eternal City, Roman Africa, etc. These images are suitable for presentations, websites and classwork and other non-commercial use.
Maecenas, Vroma and Imagines Locorum Romanorum Antiquorum are 3 sources for free, non-commercial photographs of Classical themed subjects. These are very good resources but be aware that some photos are scans or web quality (meaning fewer pixels for faster download, which means they may not enlarge well.)