In his delightful travel guide for time-travelers to Ancient Rome, Ancient Rome on Five Denarii a Day, Philip Matyszak writes (describing Caesar’s Temple): “… And among the numerous statues and works of art are two paintings by Apelles, one of the greatest artists of antiquity.”
This painting, a mural from Pompeii, is believed to be based on Apelles’ Venus Anadyomene, brought to Rome by Augustus.
Apelles was the only painter allowed to paint Alexander the Great. Wikipedia has an article on Apelles (as usual handle with care), and LacusCurtius writes about Apelles and Protegenes. He cites Pliny (Natural History, XXXV.79):
“But it was Apelles of Cos who surpassed all the painters that preceded him and all who were to come after him....He singly contributed almost more to painting than all the other artists put together....His art was unrivalled for graceful charm, although other very great painters were his contemporaries.”