Who created the image? Why was the image made? How was it created? Paint, sculpture, drawing, computer design? Why are certain characters, settings, lines, shapres, persepctives, and colors used? What do these elements communicate to the viewer? What was happening in history when the image was made? What do the pictures communicate about issues of gender, race, and class?
You will probably have to consult criticism--secondary articles and books about the image--to help you answer all of these questions.
For great ideas on interpreting images that you find, please see the History Matters page from Curtis, and this page from Library of Congress.