The bit I don’t understand is why would an omnipresent being...

The bit I don’t understand is why would an omnipresent being design us in its own image?
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First of all God is not omnipresent. He resides in a realm outside of the physical universe as shown by Solomon's prayer as he dedicated the temple.
(1 Kings 8:27) “But will God really dwell on the earth? Look! The heavens, yes, the heaven of the heavens, cannot contain you; how much less, then, this house that I have built!

Where being created in God's image is concerned we see that, unlike animals, humans were designed with the capacity to develop the qualities that God has. In our present sinful state we fall well short of the mark. But we can still work toward imitating God's personality.
(Colossians 3:9, 10) Do not lie to one another. Strip off the old personality with its practices,  and clothe yourselves with the new personality, which through accurate knowledge is being made new according to the image of the One who created it,

God is not a physical being like us. We are not spirit persons but we have the potential to become spiritual persons by taking in ''accurate knowledge'' found in the Scriptures.

There is lots of life beyond this rock. The Devil and many other angels have chosen to rebel against God and are bent on enticing mankind to join them. They are responsible for the propaganda that is spread by false religion. The Google definition 2 is:
''a committee of cardinals of the Roman Catholic Church responsible for foreign missions, founded in 1622 by Pope Gregory XV.''

(1 John 5:19) We know that we originate with God, but the whole world is lying in the power of the wicked one.