That would be symbol cut off from the source. The words of the Ten Commandments are part of a larger Word about a God who chooses a people to be a blessing to all nations, and calls them into covenant relationship. To tack the words on the wall without relating them to the story of God's love affair with humanity is to turn the words into talisman. We might as well nail a horseshoe above the door instead. It's cheaper and probably constitutional.
Ritualism is always a danger.
There have been times in the Church's history when we have separated the sacraments from the story which they are meant to tell, and from the promises of God they are meant to seal. Part of what it means to be Reformed is to guard against such abuses of the sacraments. But sacramental idolatry is not the greatest threat facing the Church today. These idols tempt us to reduce the gospel to that which we can exploit, manipulate, or comprehend. The truth is, the gospel will not bow to any idol, ancient or modern.