There are orante figures depicted on the walls of the very earliest Christian catacombs of Rome. The orantes are praying females or males. (Century and number of images of orantes: first: 0, second: 5, third: 57, fourth: 92, later: 3)* What are the orantes in the catacombs?
I suggest that the orantes represent people who were devoted to a religious life, over and beyond the ordinary congregant. They chose to be represented to the living visitors to the catacombs in the attitude of prayer. I suggest that some of the orante figures were the “consecrated virgins” or pious widows or deacons of the congregations. (There are not yet monastic orders–at least in Rome–so a devoted religious person cannot represent themself by a distinctive costume.)
Perhaps also, pious people who had not made their wishes for representation known were depicted as orantes.
It is interesting that the orante image is a graven image. That is, it represents a real human person. I suggest that the orantes derive from the Roman custom of representing real persons (mainly in sculpture) on tombs, or the Egyptian custom of representing real persons in tomb paintings. I suggest that the popularity of the orante image tracked directly with the number of Gentile-born members of the Roman congregations. I suspect that Judean-ethnic members would have still felt that such images were not appropriate for them.
*Lamberton, Clark D. “The Development of Christian Symbolism as Illustrated in Roman Catacomb Painting.” American Journal of Archaeology 15, no. 4 (1911): 507-22. DOI: 10.2307/497187.
revised January 25, 2021