This is my favorite of Edward Burne Jones' works. It is not one picture, but a series of six paintings, based on the six days of creation. Each of the angels, beginning in the first picture with one solitary angel, holds a globe showing a part of God's creative work. As we come to days 5 and 6, we see a whole gang of angels with their globes. The paintings present a glorious mass of feathers and robes.
The picture would seem to assume that the angels were created before the creation week. I believe that to be a valid conclusion. Angels are not part of this world, this cosmos. They are of a different, heavenly order.
One questionable feature of the picture is the sea shells on the ground beneath the angels' feet. Is Burne Jones advocating the Gap theory? I do think that there are very strong biblical arguments for a gap between Genesis 1:1 and 1:2, but I would not use the Gap theory to explain the fossil record. That only leads to confusion.
4 Where wast thou when I laid the foundations of the earth?
Declare, if thou hast understanding.
5 Who hath laid the measures thereof, if thou knowest?
Or who hath stretched the line upon it?
6 Whereupon are the foundations thereof fastened?
Or who laid the corner stone thereof;
7 when the morning stars sang together,
and all the sons of God shouted for joy?
The angels were joyful witnesses of God's creation. They were created to worship God and to adore Him forever and they delighted in His work of creation.
Let me quote Erich Sauer:
Thus this, so to speak, circular movement from God to God, which for earth and mankind has been given Divine revelation in the Biblical history, unfolds itself at the same time against a cosmic universal background. The starry world of God encircles the events of earth. The worlds of suns and stars, which on a cloud-free night, out of a dark, blue-black firmament sparkle upon man's earth, are in a certain sense cosmic world-frames, observers and partakers of that which here below comes to pass frm God.
Ezekiel saw the four Living Beings as they bore, as it were the throne chariot of God; and John saw them as representatives of the whole worshipping creation, surrounding in eternal praise the throne of the Most High. In the highest view this whole symbol will declare that God is the Lord of the universe. Everything should serve Him. The whole realm of created things, in its members, heads, and representatives, should be subject to Him and should glorify Him, and in this sense the whole universe, as one entire kingdom of God, forms at the same time the cosmic background of God's saving acts on earth.
Erich Sauer, From Eternity to Eternity, p.16