Do I have an opinion on the Ancient of days icon? Why, yes I do. Leaving aside my rather conservative approach to iconography, I'll let the article speak for itself. You might also enjoy reading Fr. John Whiteford's article on the topic here.
(Orthodox Arts Journal) - The essential questions in this passage and for the image of the Ancient of Days are these: Who is the Ancient of Days? And who is the Son of Man who comes close to him to receive a kingdom? This passage from Daniel has historically been used to theologically justify images of God the Father, alone or in various forms of what is called the New Testament Trinity as opposed to the Old Testament Trinity that is the Hospitality of Abraham. The so-called New Testament Trinity has various forms but always shows an old man with a white beard, an adult man or a boy, and a dove. According to this interpretation, the old man, the Ancient of Days, is the Father; the man, the Son; and the dove, the Holy Spirit. These images and their theological justification have become so common in the Orthodox world that nobody, almost nobody, questions them. But I, being impertinent, rebellious, and–imagine Orthodox, I hope–wish to rise up and challenge both the image and the theological explanation as being contrary to the Holy Tradition.
We know from historical and iconological studies that both the image of the Ancient of Days as God the Father, alone or in the so-called New Testament Trinity, and its theological justification based on Daniel do not come from the Orthodox Church’s tradition. It is only around the late Middle Ages that the image and its justification make their appearance in the Orthodox world, and the source is the Latin Catholic West. For several centuries, western painters had been painting various forms of the Trinity, which were eventually justified by an appeal to Daniel and his vision of the Ancient of Days. During the period of what is called the Western Captivity, when Orthodox all over the world swallowed nearly everything that came from the Latin West as “better” than the “old-fashioned” Orthodox images and theology, this image and its justification made great inroads into the Orthodox consciousness. And this to such an extent, that people forgot the real and genuine Holy Tradition of the Fathers. And what is that Tradition?
Briefly, it is that the Logos of God the Father, the Son, who became incarnate in the historical Jesus of Nazareth, is the one, the Person, who reveals himself, imperfectly, vaguely, as through a mirror, just a little bit, in the Old Testament. Who spoke to Moses on Mount Sinai? Who spoke to him in the burning bush? Who is the creator that Genesis talks about? With whom did Adam and Eve walk and talk in the Garden of Eden? Whom did the prophets see and hear in their visions? The unanimous Holy Tradition of the Orthodox Church says that it was the Divine Logos, the Son, the second Person of the Trinity, not the Father. The Son reveals the Father and the Spirit both in the Old Testament, “darkly” and openly in the New Testament. “And he taught us how the Law and the Prophets spoke about him.” So the question is this: Whom did the prophets, and particularly Daniel, see in their visions? The general answer from the Fathers is that they heard and saw the Son and not the Father. Therefore, this general principal of interpretation–the Son reveals himself darkly in the Old Testament–should be enough to answer the question as to the identity of the Ancient of Days...