
Scholar of early Christian art Martin Stoll makes some intriguing comments about portrayals of Christ in apse-spaces in early Christian Churches. But his focus is not restrictive, and he applies what he is saying to other Christian holy spaces (such as those in the Catacombs). He is open to a pre-Nicene date for Cubiculum 54 in the Catacombs of Marcellinus and Peter, which has an early representation of the enthroned Christ with arms outstretched to teach those below Him. If the earlier date is correct, it would imply the existence of a pre-Nicene apse-like portrayal of Christ—in his words “a theophany to the viewer”:
“Gestures are an important part of the representations in multi-figured compositions, as they indicate matters of rank, the actions the figures realize in relation to each other, but also in relation to the viewer. This last element is particularly important in early Christian iconography, as many apses of early Christian churches were meant as a theophany to the viewer, and especially the gestures of Christ (often represented in a very frontal way) seem to address the viewer of the compositions…
What is nowadays more commonly known as a blessing, used to be more assimilated to a teaching symbol in late antique culture 378 . Many late antique philosophers were depicted in this way, such as on the sarcophagus of a married couple in the Museum of Konya (fig. 209). Christ would subsequently have been represented in a similar fashion, such as the Christ as teacher sarcophagus of Sant’Agnese fuori le mura (fig. 210), or in the Christ of the catacombs of Domitilla (fig. 181).”
Martin Stoll, Painted Iconographical Programs in Late Antique and Early Medieval Churches: Continuities and Ruptures with Greco-Roman Decors (3rd century A.D. - 6th century A.D.), page 60