Like the previous portrait of Bacchus, he’s accompanied by his cult items, a caduceus, rooster, and in this case, twin tortoises.

The thrice born, the God that comes, also hailed as Zagreus, Sabazius, Liber, and Dionysus, the outsider, the wanderer, feared and suspected wherever he roams, the center of mystery, preaching divine ecstasy through heightened senses, ripped apart by Titans only to surge again from the earth whole again like Osiris, like wheat sprung from a fecund field, like plump, crimson grapes that hang from a curling vine.

https://en.wikipedia.org/wiki/Dionysus#Mythology