God is invisible to us. I rather suspect He is invisible also to people in the Spirit world—perhaps also to those who reside in Mount Zion, the heavenly Jerusalem.
It appears likely that the four living creatures, the cherubim, portray in external form the Nature of God, with their four faces–the lion, the ox, the eagle, and the man.
The following passage gives us some insight, I believe:
Beyond all question, the mystery of godliness is great: He appeared in a body, was vindicated by the Spirit, was seen by angels, was preached among the nations, was believed on in the world, was taken up in glory. (I Timothy 3:16)
The "body" is that of the Lord Jesus Christ. I suppose that many would derive from this passage that God is one Person in three manifestations–as Father, Son, and Holy Spirit. While a certain part of this understanding is true, in that God is in all Three, yet it is clear enough from the New Testament that there are three distinct Persons, three wills, in the Godhead. "Not My will but Yours be done."
If we do not perceive that there are three Persons in the Godhead we will not understand God's plan to increase the revelation of Himself in the saints.
