Zeus throwing a thunderbolt, more than 2450 years old, fished out of
Cape Artemisium in 1928, now an icon of Greece.
Athens, Archeological Museum bronze, 210cm

This bronze satyr killing a snake, 44 cm high and 2350 years old, is from the mysterious civilisation of Etruria in northwestern Italy. He originally supported a large vase. Unlike most satyrs, his penis is neither outsized nor erect.
Wittelsbacher Ausgleichfonds, Munich

On this bronze Etruscan pot from Pareneste (Palestrina), wing-heeled
Hermes brings three goddesses to Paris (seated) for his judgement. The 63cm high pot is finely detailed

late 4th C BCE, Rome, Villa Giulia

This terracotta vase was made in eastern Greece (probably on the island of Rhodes) 2500 to 2550 years ago. Phallus vases are a rare and distinctive kind of archaic Greek pottery. They were used to store perfumed oils, presumably for erotic or medicinal purposes. Archaic Greek potters sculpted vases in a wide variety of shapes, including human heads, legs, and animals. These "peniform" vases reflect a playfulness and unselfconsciousness about eroticism that recurs throughout Greek Art, but regardless of what this represents, it is a gloriously harmonious shape.

This 2500-year-old Greek satyr's penis is comically large, his foreskin
still covering most of his glans. Nymphs beware!

National Archaeological Museum, Athens

This amphora, painted by Euthymides, son of Polias, over
2500 years ago, was found in Vulci in Etruria.

Staatiche Antikensammlungen, Munich
Why so small?
"The artistic evidence implies that over-large genitals were considered aesthetically unpleasing by the Greeks and Romans. ...the ideal type of male beauty epitomised in classical sculpture, Greek and Roman, normally depicts genitals of somewhat less than average size...certainly never more. Consequently, the exaggerated genitals of Priapus made him seem an ugly and grotesque figure, though benevolent. "Sex or Symbol?Erotic Images of Greece and Rome"Catherine Johns

We should never assume that the Greeks, Romans and Etruscans considered images of penises as we do.
They used them on amulets to ward off the evil eye, with no more thought for sexuality than we consider crossed fingers to be a Christian symbol.
The faces of people on bowls are almost invariably in profile, but we do not suppose that full-face was considered "aesthetically displeasing".
So the small penises shown on ordinary mortals may have been no more than a convention, to distinguish them from fertility figures such as satyrs and Priapus - which were much more significant in an age when the fertility of plants, beasts and people could not be taken for granted or brought under human control by material means.

Roman gold amulet, 1st century CE, about 1cm across
British Museum

Why always covered?
The Greeks considered only the glans, not the whole penis, to be obscene. In the gymnasium, men kept their glanses out of sight by tying a thong (kynodesme) around their foreskins, and Hellenised Jews sought foreskin restoration to make that possible. The "red-tipped" phallus that the Chorus of The Clouds disdained would have belonged to a circumcised Egyptian (leather intact phalluses were part of the costume in all comedies, including The Clouds). The glans was only shown on purely phallic images, such as those used in religious festivals. On those, the artists showed wrinkling to indicate the foreskin.

Even on the point of penetration, erotic images showed the foreskin as fully forward. A red-figure jug by the Shuvalov painter, 2400 years old.
Berlin Antikenmuseum