Cyprian:
The Roman sculptures from the 4th century do depict the Trinity. But sculptures are not allowed in Orthodox Church by way of the Council of Trullo (the 6th Council) three hundred plus years later.
My only possible objection to the Trinity ikon is the insertion of a triangle within the ikon. It is a matter of debate whether this is a Latin innovative insertion into an otherwise Orthodox ikon. I also have no problem with the Trinity ikon (from St. Andrew Rublev) which is another symbolic rendering of the Trinity via the three angels visiting St. Abraham and Sarah.
Christ was also energetically and symbolically depicted as a fish in many catacomb paintings in the 1st and 2nd centuries. Do you know of any ikons of fish in GOC churches nowadays? I do not think so. There are none in RTOC churches that I have been in.
A sculptural aside
Christ was 3D rendered sculpturally (according to Eusebius) in the 4th century outside of a church in the East but 3D sculpture was forbidden in 681 in the East. It was ignored in the West where 3D sculptures adorned churches from 681-1285..., mainly on the exteriors of churches. After 1285 many of these 3D sculptures moved into Latin churches.
If the Latins come back to the Church in the future, will the TOC's demand the destruction of all Latin 3D sculptures starting with the Rondanini Pieta? Do we take the hammer to the Rondanini Pieta first or do we first take care of the demons Apollo and Athena first?
Although 3D sculptures of Christ inside or outside of Churches in the East were forbidden after 681, in absolute hypocrisy, all three Romes (Constantinople, Rome and Moscow) both before and after 681 littered their cities, palaces and domains with 3d sculptures of the demons Apollo, Athena, Zeus etc. (St. Athanasius the Great: "the gods of the pagans are demons.") But these demons were not allowed in churches. Plethon composed a liturgy to the demon Zeus in the 15th century and was invited to take the boat to Florence in 1439 to the Council with the Tsar and his bishops. Was he ever condemned for this liturgy by the Greek Church?
I bring the idea of 3D sculpture up in that you brought up the 4th century Roman sculpture as proof of ikons related to the Trinity. But it was not an ikon, but a sculpture on a tomb. I have seen 3d sculptures of saints in Kiev (Vladimir and Anthony and Theodosius of the Caves). All three would never be allowed in Orthodox Churches today.
It is a slippery, sculptural slope into the possible realm of the Orthodox version of the Taliban (who recently destroyed all the Buddhas in Afghanistan) if we ever get temporal power again in this world.
Would the Rondanini Pieta be safe from the future theological hammers of the TOC's in that it is in a museum in Florence along with the Trinity sculpture of the 4th century which in a Roman museum?
Christ verbally circumscribed the Essence of God as Father throughout the New Testament. The Creed verbally repeated what Christ did.
In ikons from Sinai in the East, God is energetically circumscribed as Father in the form of the hand of God in the right hand corners of many ikons. The Essence of the Holy Spirit is energetically written on ikons in the form of a dove.
Because of the extent of the destruction of ikons from 717-843 we do not know the extent of the Trinity ikons within the eastern half of the church prior to 843.
The Ancient of Days appears energetically as the 2nd Person of the Trinity (the Son) to St. John at Patmos and as God the Father energetically to St. Daniel in the Old Testament Both can and should be venerated. That is my view.
But my point is that there are scholars who disagree about this. To really understand, agree or disagree with their point of view they must be read. I am not an expert. It would be helpful if a bibliography of both sides would be inserted on this site so that the normal reader here can consider both sides (or more sides than that) and decide for themselves. I have read a few books on both sides but am not an expert.
It is apparent you have studied this issue more than me but I am not sure you are an expert and/or have published works supporting your view which have been reviewed by other historical experts in this field.
As far as ikonoclasm (the destruction of ikons and persecution of people and churches because of those ikons), it is a stretch to extend that term (the destruction of ikons) to some of the usual suspects involved on this site in my view.
Cyprian, Thank you for taking the time to present your point of view. I learned a great deal reading it.
. The demon of Reason.