In the back of the Concordant Literal New Testament, Knoch defines image (Greek word: eikon) as simulate. Here's the definition of simulate as found at dictionary.com:
1. To have or take on the appearance, form, or sound of; imitate. To make in imitation of or as a substitute for.
2. To make a pretense of; feign: simulate interest.
3. To create a representation or model of (a physical system or particular situation, for example).
David Guzik wrote the following:
He is the image of the invisible God: Image (the ancient Greek word eikon) expresses two ideas. First, likeness, as in the image on a coin or the reflection in a mirror. Second, manifestation, with the sense that God is fully revealed in Jesus
i. If Paul meant that Jesus was merely similar to the Father, he would have used the ancient Greek word homoioma, which speaks of similar appearance.
ii. “God is invisible, which does not merely mean that He cannot be seen by our bodily eye, but that He is unknowable. In the exalted Christ the unknowable God becomes known.” (Peake)
