The standard understanding of "image of God" has nothing to do with physical traits. It refers to humans having attributes of God's character, such as agency, concience, etc.
Naturally you believe that the book of Genesis with the creation account is mythical, I concede that you believe that. I, as you know, do not contest the veracity of the account. And will not, no matter how people want to put it. However, remember -- and this is an important point to me, although not explored, but the tree of knowledge of good and evil was placed in the Garden that Adam and Eve were privy to -- and told really that the tree, although they COULD take from it, was not to be eaten of. Thus, although made in the image of God, He let them know He was their guide and mentor. God does not die. But they, Adam and Eve, could and did die. But then again -- not to get into a big discussion now about this, there IS throughout the scroll the hope of (1) the Messiah,, and (2) everlasting life -- reversing what Adam and Eve did. Shalom.