"(4) If the image of God refers to some moral principles which are born in us and with us and which consist in some tiny remnants of the divine image in the mind and will of man, then too with regard to these most minute particles we maintain that the image of God was not utterly lost. In fact, the work of the Law is still written in the hearts of men, even of the unregenerate.
(5) But if, according to its scriptural understanding, the image of God refers primarily to that righteousness and holiness, integrity and uprightness of all faculties, in which man was originally created then it must be said that the image of God was lost indeed through the fall." (Pg. 62)
So the image of God is not the soul itself. Rather it is that which was lost in the fall, the righteousness, and holiness, integrity and uprightness of all faculties, and even immortality (pg 46). These then are restored to us in Christ.
It is in the soul that Adam and Eve bore the image of God, and to the soul remain even after the fall a Modicum of spirituality, intelligence and free will, we still exercise dominion over the animals of the earth. Yet, insofar as we tend to use these things for evil and sinful ends, the image of God is lost.