Heaven is a wonderful place. God created heaven. It has been stated that only four angels have seen God.
Known inhabitants
God
Jesus
Seraph
Archangels
Angels
Known angels
Lucifer
Zachariah
Anna Milton
Uriel
Castiel
Unnamed or unidentified angels
Known archangels
Zachariah (Unconfirmed?)
Michael (Defeated Lucifer)
Gabriel (This angel has yet to make an appearance in this show)
Raphael (This Angel has yet to make an appearance)
Lucifer (At one point Lucifer was an archangel)