NOTE: The artist colored the circled wing angel below the Throne brown denoting earthly color. Biblically, Lucifer after his fall was cast down to earthly realm. A color contrast with the color of wing cherub on left & right side is artist way of conveying the difference of Angelic glory.
In closing, the artist perfectly describes what is the "Divine Plan of God"existed in eternity represented by three concentric circles symbolizing the Holy Trinity inside the Third Heaven. We can see that the artist included the Ark of the Covenant here plus Lucifer being the bearer of God's Light or guardian of God's Throne in the Holy Mountain. The Five Characters (Abba Father, Jesus Christ, Holy Spirit the "another Advocate & Spirit of Truth, Mary the Theotokos and Lucifer which is created good and bestowed with perfect gifts & anointing) are the main actors in the Drama of Man's Salvation.