From a Christian perspective, this passage is typically not seen as God and humanity sharing biological traits. One example, taken more or less at random, is this statement from Answers in Genesis:
Man in the image of God; what does this mean in practical terms? It cannot refer to bodily, biological form since God is a Spirit and man is earthly.
So what can the phrase mean? Here is Jesus on the topic in Mark 12:13-17 (HCSB):
Then they sent some of the Pharisees and the Herodians to Him to trap Him by what He said. When they came, they said to Him, "Teacher, we know You are truthful and defer to no one, for You don't show partiality but teach truthfully the way of God. Is it lawful to pay taxes to Caesar or not? Should we pay, or should we not pay?"
But knowing their hypocrisy, He said to them, "Why are you testing Me? Bring Me a denarius to look at." So they brought one. "Whose image and inscription is this?" He asked them.
"Caesar's," they said.
Then Jesus told them, "Give back to Caesar the things that are Caesar's, and to God the things that are God's." And they were amazed at Him.
Jesus' answer works on two levels:
- Tax is due to Caesar because he established the monetary system.
- Since people are in the image of God (via Genesis 1), they belong to Him.
Note that coins don't have all the qualities of Caesar. They don't have bodies, but only faces. They don't have authority to command armies, make laws, raise taxes, enforce justice, etc., but they represent a portion of that authority. They are not themselves worshiped, but ought to be respected. Jesus managed to escape their trap with considerable skill in applying the Torah.
However, orthodox Christianity also believes that God became man and through Jesus redeemed and perfected the image of God. Colossians 1:15-20 (HCSB):
He is the image of the invisible God,
the firstborn over all creation;
because by Him everything was created,
in heaven and on earth, the visible and the invisible,
whether thrones or dominions or rulers or authorities—
all things have been created through Him and for Him.
He is before all things, and by Him all things hold together.
He is also the head of the body, the church;
He is the beginning, the firstborn from the dead,
so that He might come to have first place in everything.
For God was pleased [to have] all His fullness dwell in Him,
and through Him to reconcile everything to Himself
by making peace through the blood of His cross—
whether things on earth or things in heaven.
In as sense, God does have all the attributes of humanity in the person of Jesus who has become the first man of the new creation as Adam was the first man of the original creation. So it's possible under a Christological hermeneutics to read Genesis 1:26 as a prophesy that was not fulfilled before Jesus. We also believe that there will be a resurrection when we all will get renewed bodies and live on a renewed earth. (See also Revelation 21.)