This is a detail from a fresco in the dome of the Karlskirche of the assumption of St. Carlo Borromeo by Johan Michael Rottmayr. Most of the fresco is saints and angels and all that, but there are a few more interesting bits, such as this:
Apparently the temptation to stick it to Luther was irresistible. All that space to paint, after all. In addition, there is scaffolding supporting an elevator and staircase that you can take up into the dome; it brings you within spitting distance of the fresco.