Here I have fleshed out most of the middle of the pack, but neither the lower end--the inconstant Horace? The youthful Epicurean Virgil contrasted with the grave imperialist Stoic poet of his maturity?--nor, with the exception of Lucretius, the top of the class; Epicurus, Metrodorus, Hermarchus, Polyaenus.
I'll sketch out my thoughts, but I have nothing solid.
- Polyaenus: "a kindly and just man" (D. L.), and a mathematician. The scales of justice, and the Canon, or measuring rod, for the geometer gone "rogue"?
- Hermarchus: the rooster and the archway; the rooster was the Greek symbol of the island of Lesbos where Hermarchus was born, and in mythology was once a young soldier whom Ares had posted at the door of the room where he and Aphrodite were otherwise occupied (some Lucretian imagery there). When Hephaistos found them out, Ares cursed the young soldier by turning him into a rooster, to raise the alarm forever at the coming of day. Hermarchus was the successor to Epicurus in the garden--the sentinel posted during a period of transition, as represented by a garden archway.
- Metrodorus: the guttered candle and the double herm. Metrodorus was born in Lampsacus on the Hellespont, the same strait of water made famous in the story of Hero and Leander, who lived on opposite sides. Every night Hero would light her lamp, and Leander would use it as a guide to swim across the sea. One night the wind guttered the lamp, and Leander lost his way and drowned. The double-herm of Epicurus and Metrodorus represents their close connection, and the guttered candle his untimely death.
- Horace: the pig and goblet. "Fat and sleek", wine-sodden poet....you get the idea.
- Plotina: the dove and the diadem. The dove as a symbol of both Venus and peace (her intercession on behalf of the Epicurean school), the diadem signifying royalty
Epicurus himself. The trickiest of the lot. Personally I like ⟐ as previously proposed here on the forum (not by me), representing atoms (the dot), void (the empty space), and the tetrapharmakos (the four sides of the diamond, and the four surviving letters of the man himself--Herodotus, Pythocles, Menoeceus, and Idomeneus). Coins of Samos often featured a lion, but more typically a bull and peacock (symbols of patron goddess Hera), and an amphora of their legendary wine.
A boat or ferry, not to shepherd souls to the underworld, but to a life beyond fear of death; a skull or memento mori, a mortar and pestle, a piglet or wild boar, a fig tree or the myrtle of Aphrodite, an Ionic column, the shattered fetterlock, or the eye raised to the heavens as in Lucretius.
The greatest symbol of all was his own portrait.