Victoriae

But in the middle of the ceiling he painted a circle with four Victoriae holding the papal crown and keys…

Source: wiktionary

The motif of Victoriae supporting a votive shield, set not against a palm-tree but on a cippus or altar, is present in major triumphal sculpture shortly before its appearance on the coinage of Constantinus I (43 f, n. 10).[…]The two reverse groupings which originate on sestertii of Hadrian (BMCCRE III, pl. 79, 7), continue through the coinage of Caracalla, and show Victory floating or standing to the left or right with a standard or trophy held crosswise and extended in the hands are nothing more than the translations of similarly arranged Victoriae from the spandrels of triumphal arches to coin reverses.

Source: wiktionary

Nike-Victoria sets up a tropaion (attaches arms, sacrifices a bull, puts on a wreath or an inscription); in Roman times two Victoriae fixing a shield to a tropaion are placed preferably in antithetical positions on the breast-plate of statuae thoracatae, Nike crowning a tropaion is found mostly on Megarian bowls, small incense-altars and victoriates, Victoria writing on the shield of a trophy is a Roman device.

Source: wiktionary

Altar of Roma and Augustus at Lugdunum, flanked left and right by Victoriae on columns.[…]Two Victoriae supporting wreathed votive shield inscribed vot x mvl xx / victoriae d d n n avgg / ·sis· in exergue.

Source: wiktionary