Yes, it is against the canons of both the Quinisext and Seventh Ecumenical Councils to depict God the Father.
Could you please quote the relevant Canons from these Ecumenical Councils which forbid depictions of God the Father? I don't think they exist, but perhaps I have missed them.
*crickets* for nearly three years.
There are no canons per say about the icon, but there is the spirit of the 7th Ecumenical council.
As Orthodox Wiki
Icons depicting God the Father do not conform to the teachings of the Seventh Ecumenical Council. God the Father is invisible and not able to be depicted. Since Christ was born of the indescribable Father, the Father cannot have an image.
Here is but one quote from the epistle of Pope St. Gregory II’s letter on the Holy Icons to Emperor Leo the Isaurian:
“Why do we not delineate and paint the Father of the Lord Jesus Christ? Because we have not seen and known Him, and it is impossible to delineate and paint the divine nature.” This epistle of St. Gregory was adopted into the minutes of the Seventh Ecumenical Council. This council stipulated that we depict only the incarnate person of Christ. God the Father was never incarnate, and was never therefore depictable as a human being, perish the thought! He is invisible to all created beings.
Let us take another quote, and this time from the great St. John of Damascus. From his book on Christological Arguments: “If we made an icon of the invisible God, we should certainly be in error, but we do nothing of the sort, for we are not in error if we make the icon of the incarnate God, Who appeared on earth in the flesh, and Who, in His ineffable goodness, lived among men and assumed the nature, quantity, shape and color of flesh.”
There are many more fatehrs who wrote ont his too, but I am not sure any Early Church Fathers wrote positively about making an icon with God the Father Shown. 1 Corinthians 10:23 "All things are lawful for me, but all things are not expedient: all things are lawful for me, but all things edify not."