In the Old Testament graven images are prohibited, yet the Church encourages crucifixes, images of the Sacred Heart, etc. I have always wondered about this. What can you tell me?
Many non-Catholic Christians use the passage you refer to, Exodus 20:4-5, to "prove" to Catholics that making "any graven images or any likeness of any thing that is in heaven above, or that is in the earth beneath" is detestable to God. But when this passage is read in context, it is not the making of images that is condemned but the worship of them.
In fact, five chapters later God commands the Israelites to make two golden statues of angels as part of the lid of the ark of the Covenant (Ex 25:17-19). That’s an image of something from heaven. Then, in 1 Kings 6, God commands that graven images of flowers and palm trees be made, as well as 15-foot tall statues of cherubim. And in Numbers 21, God commands that a bronze serpent be made and uses it to heal the Israelites. It was preserved for 800 years and then destroyed when some began to worship it (2 Kgs 18:4).
Catholics do not worship statues, because only God is deserving of adoration. The Catechism of the Catholic Church is adamant in affirming this (CCC 2112–2114). When a Catholic bows to a statue, he is not worshiping it any more than King Solomon worshiped Bathsheba when he bowed to her in 1 Kings 2:19. In other words, the honor given to images does not detract from the honor that is due to God. After all, if one member of the body is honored, the others should share in its joy (1 Cor 12:26).
If someone enters your house, he should expect to find a picture of your mother. So, when someone walks into a Catholic Church—the household of God—he should not be surprised to find a picture of the mother of God, along with the rest of the heavenly family!
In giving the Israelites a beautiful temple strewn with images (1 Kgs 6), God acknowledged the reason why he gave us our senses: to use them to worship him in spirit and truth.