The second commandment is necessary because people cannot always keep the first one.

During the days of Moses a lot of people wanted to see what they worshiped so they would make something , even the Israelites did this with the golden calf.

People would offer all kind of sacrifices to these made up God's including human ones.

They would make golden statues of earthly rulers that they had seen and worship them.

God has never been a tangible being[Deut4:12]but he is always a Spirit[John4:24]

The complete commandment goes as follows [from the Jewish bible].

You are not to make any God's before me. You are not to make for yourselves a carved image or any kind of representation of anything in heaven above, on the earth beneath or in the water below the shoreline.

You are not to bow down to them or serve them;for I ADONAI your God, am a jealous God,punishing the children for the sins of the parents to the third and fourth generation of those who hate me but displaying grace to the thousandth generation of those who love and obey my mitzvot.

There is no actual separation between 1 and 2 in the Jewish text but were separated in ours.

We may not make a carved image or offer sacrifices but some do worship entertainers or icons in the world and sacrifice time and finances and other things instead of making them to God.

During the reformation the soon to be called Protestants went into the Catholic churches and took all the statues of Christ and Mary and all the others and replaced them with copies of the Ten Commandments.

I see no problem in pictures and statues for I have a few pictures of my own I just don't worship them.

We are not to worship God's creation or anything man creates about God but God himself.