The more one knows, the more confusing it can be!
Sometimes artists would give the physcial features of the reigning pope to the historic pope who figured in the event being portrayed. It was an "honor thy father" thing, or ... perhaps more likely ... a sycophant thing. As one gains more experience viewing art, one might come to recognize, from contemporary portraits, what, say, Clement VII looked like. So one might be a tad confused whan looking at Giorgio Vasari's Mass of St. Gregory the Great (1540), in the Pinacoteca Nazionale in Bologna. ... St. Gregory (590-604) happens to look exactly like Clement VII (Papacy: 1523-1534)!
It was also common for an artist to depict his patron in a history painting, but viewers today are less likely to recognize a mere cardinal!