In question 210 of his Amphilochia (PG 101:947-952), St. Photius takes on an objection from those opposed to icons:
Those who are most audacious and wicked among the iconoclasts, and who consider vain curiosity to be wisdom, ask what is the true image of Christ, whether it is that which the Romans draw, or that which the Indians, or the Greeks, or the Egyptians portray, since these do not agree among themselves in likeness … [Later on Photius repeats the objection:] They say that, seeing as the Greeks endeavor to have Christ similar to themselves, the Romans instead to themselves, the Indians to their own figure, and the Ethiopians to theirs … it is not apparent from these things who might be taken for the true Christ.
St. Photius gives six objections that can be used against this argument.
What is first to be said to them is: from that very assortment of images whence you propose to indicate a conflict, you unwillingly admit that, throughout the world wherever Christianity exists, the existence and cult of images is to be had. Thus in that which they desired to destroy, they confirm even more the images, and they are caught enmeshed by their own reasoning.
The second, third, and fourth objections are pretty similar. Essentially, Photius argues that this reasoning could equally be applied to the differences in the gospels and liturgies between different cultures, which would lead to the absurd result that these are not legitimate either. Furthermore, it even applies to the crosses which the iconoclasts set up, some of which have a title, others not. In the fifth objection he argues (I admittedly found it difficult to follow) that anyone who attacks an image necessarily is targeting the one depicted in the image. In the final thing which St. Photius adds, he writes:
The dissimilitude which is observed among images does not void the nature and truth of the image. For the thing depicted is not expressed only by the figure of the body and the form of the colors, but also by its disposition, its harmonious action, its emphasis of passions, its dedication in holy places, by the explanation of its inscriptions, and in other more prominent symbols which should not at all (or at least for the most part) be absent in the images of the faithful. Through these things, no less than if everything were present, we are lead to the memory and honor of the thing depicted, which is the purpose of iconography.
St. Photius’s list of the components of an image which give it meaning has its own interest (note that he remarks that the location of an image is part of what gives it its meaning). But what I find most remarkable about this is, first, the topic, which is still discussed today (e.g., whenever someone asks why Jesus is often depicted as white), and, second, St. Photius’s response. It is not triumphalist, i.e., dismissing the Indian, Egyptian, or Ethiopian depiction of Christ as erroneous. Indeed, he acknowledges that each culture depicts Christ in its own way. But he remarks that this is no less astonishing than each culture having gospels in its own tongue and modes of expression, or its own liturgies; for these things, each suited to a different culture, express their truths no less than if they were only expressed according to one way.