So be it, Lord; Thy throne shall never,
Like earth’s proud empires, pass away:
Thy kingdom stands, and grows forever,
Till all Thy creatures own Thy sway.
We quite often refer to God as king and to God’s kingdom or the kingdom of God, but we almost never refer to God as emperor or to God’s empire or the empire of God, even though King of kings and Lord of lords is more analogous to an earthly emperor than a king.
The only reference to empire/emperor/imperial in the King James/Authorised version of the bible is in the comparatively late OT book of Esther (1:20):
When the king’s decree which he will make is proclaimed throughout all his empire (for it is great), all wives will honor their husbands, both great and small.
Of the other 27 translations on Bible Hub, one uses realm, four use empire and the rest kingdom.