My uneducated feeling is that this is a reference to the tabernacle. Just as Aaron's rod, the manna and the tablets are represented on our altar, so also we might represent the Cherubim, between whom sat God, upon the mercy seat, for now God is revealed through Christ, who sits upon the mercy seat of the Theotokos and speaks through the Gospel, not out of thin air.
Exo 25:18 And thou shalt make two cherubims of gold, of beaten work shalt thou make them, in the two ends of the mercy seat.
Exo 25:19 And make one cherub on the one end, and the other cherub on the other end: even of the mercy seat shall ye make the cherubims on the two ends thereof.
Exo 25:20 And the cherubims shall stretch forth their wings on high, covering the mercy seat with their wings, and their faces shall look one to another; toward the mercy seat shall the faces of the cherubims be.
Exo 25:21 And thou shalt put the mercy seat above upon the ark; and in the ark thou shalt put the testimony that I shall give thee.
Exo 25:22 And there I will meet with thee, and I will commune with thee from above the mercy seat, from between the two cherubims which are upon the ark of the testimony, of all things which I will give thee in commandment unto the children of Israel.
1Sa 4:4 So the people sent to Shiloh, that they might bring from thence the ark of the covenant of the LORD of hosts, which dwelleth between the cherubims: and the two sons of Eli, Hophni and Phinehas, were there with the ark of the covenant of God.
I also had a feeling about Revelations, but couldn't find any reference to Cherubim there - only angels...