Image of God: A Royal Vocation

"Then God said, 'Let us make man in our image, after our likeness. And let them have dominion over the fish of the sea and over the birds of the heavens and over the livestock and over all the earth and over every creeping thing that creeps on the earth.'" (Genesis 1:26, ESV). This is not, first of all, a claim about human intelligence or inner moral sense. It is a royal commission spoken over humanity at the very dawn of creation — an appointment to an office, not merely a description of a nature.
In the ancient world, an "image" (Hebrew tselem) of a god was a physical object placed inside that god's temple to represent the deity's presence and authority there. The image did not need to think or feel the way the god thought or felt; it needed to function as the god's authorized stand-in, the visible sign that this territory belonged to that god and answered to him. Genesis places the first humans in a garden pictured throughout the text as God's own sanctuary, and it makes them, together, his tselem: his living representatives, set there to extend his ordered rule outward into the wider earth. Genesis 1:28's command to "have dominion" and "subdue" the earth is not a separate afterthought bolted onto verse 26 — it is the functional content of what bearing the image actually means. Humanity was never installed in the garden merely to admire it; humanity was installed to rule it, under God, on God's behalf.
This is why the psalmist can marvel, almost in disbelief, at the scale of what was given: "Yet you have made him a little lower than the heavenly beings and crowned him with glory and honor. You have given him dominion over the works of your hands" (Psalm 8:5-6, ESV). The image of God was never a private possession or a philosophical puzzle to be solved. It was, and remains, a crown — set on the head of every human being, from the very first page of Scripture, as the sign of a vocation nothing since has revoked.