In the laws given to the early Israelites we find:
Leviticus 19:4 (NIV) 4 “‘Do not turn to idols or make metal gods for yourselves. I am the LORD your God.
This we probably get, but we also find this:
Exodus 20:4 (NIV) 4 “You shall not make for yourself an image in the form of anything in heaven above or on the earth beneath or in the waters below.
So no idols - observe not just no metal gods, but no metal images of God - so what is an image or icons in this regard? Think perhaps of computer icons, things to look at that remind us of God, that help us think of God.
So why this instruction against making things in his likeness? Because he has already done it for us:
Genesis 1:27 (MSG) 27 God created human beings; he created them godlike, Reflecting God’s nature. He created them male and female.
So why no idols? I think because God wanted us to see that if we want to look at something to remind us of God we only have the option of looking to the person sat on your left and your right!