"...Chocolate Frogs have cards, inside them, you know, to collect -- famous witches and wizards. I've got about five hundred, but I haven't got Agrippa or Ptolemy."
-- Ron Weasley (PS6)
Claudius Ptolemy was a Greco-Roman Egyptian geographer and astronomer. On their first train-ride to Hogwarts, Ron was hoping to get a Ptolemy Chocolate Frog Card (PS6).
Other canon notes and references
No actual image exists of Ptolemy's Chocolate Frog Card, either in the video games or on Pottermore.
Ptolemy lived in Alexandria, a great city in Egypt founded by the Greek leader Alexander the Great, but ruled by the Romans in his time. That is why his first name is Latin, and his last name is Greek. He wrote books on mathematics, geography, science, and astronomy.