“Had posterity been enabled to have several such representations executed during the first century when the figure, dress, and everyday habits of the Reformer were still fresh in the memory of his contemporaries, perhaps the Christian world would be more Christ-like; the dozens of contradictory, groundless, and utterly meaningless speculations about the “Son of Man” would have been impossible; and humanity would now have but one religion and one God. It is this absence of all proof, the lack of the least positive clue about him whom Christianity has deified, that has caused the present state of perplexity.
No pictures of Christ were possible until after the days of Constantine, when the Jewish element was nearly eliminated among the followers of the new religion. The Jews, apostles, and disciples, whom the Zoroastrians and the Parsees had inoculated with a holy horror of any form of images, would have considered it a sacrilegious blasphemy to represent in any way or shape their master. The only authorized image of Jesus, even in the days of Tertullian, was an allegorical representation of the “Good Shepherd”, which was no portrait, but the figure of a man with a jackal-head, like Anubis. On this gem, as seen in the collection of Gnostic amulets, the Good Shepherd bears upon his shoulders the lost lamb. He seems to have a human head upon his neck; but, as King correctly observes, “it only seems so to the uninitiated eye.”
On closer inspection, he becomes the double-headed Anubis, having one head human, the other a jackal’s, whilst his girdle assumes the form of a serpent rearing aloft its crested head. “This figure”, adds the author of the Gnostics, etc., had two meanings – one obvious for the vulgar, the other mystical, and recognizable by the initiated alone. It was perhaps the signet of some chief teacher or apostle. This affords a fresh proof that the Gnostics and early orthodox (?) Christians were not so wide apart in their secret doctrine.
King deduces from a quotation from Epiphanius, that even as late as 400 A.D., it was considered an atrocious sin to attempt to represent the bodily appearance of Christ. Epiphanius brings it as an idolatrous charge against the Carpocratians that “they kept painted portraits, and even gold and silver images, and in other materials, which they pretended to be portraits of Jesus, and made by Pilate after the likeness of Christ. These they keep in secret, along with Pythagoras, Plato, and Aristotle, and setting them all up together, they worship and offer sacrifices unto them, after the Gentiles’ fashion.””
H. P. Blavatsky
The Mark Of God: Understanding Your "I AM Presence" 