Is it sinful to adorn our bodies by piercing and tattooing?
First of all we need to look at a couple of scriptures, so read them carefully. "And if the servant shall plainly say, I love my master, my wife, and my children; I will not go out free: Then his master shall bring him unto the judges; he shall also bring him to the door, or unto the door post; and his master shall bore his ear through with an aul; and he shall serve him for ever." (Exodus 21:5-6) "Ye shall not make any cuttings in your flesh for the dead, nor print any marks upon you: I am the LORD." (Leviticus 19:28)
In the first scripture, the man's ear was pierced as a symbol that he was a bond servant for life. It was permanent and set the status of the man for the rest of his life. The intent of the piercing was to let whomever know that he was a servant in his master's care. Nothing sinful was attached to the piercing.
This, however, is the only event that God said to pierce a person's body. Also, I find no mention of an earring or other object being inserted in the pierced area. An earring or such would only draw attention to the servant. Getting attention is not why the piercing was done. Do you see the wisdom in what God said and did not say?
Now, the second scripture has to do with cutting and marking the body. The cutting God refers to was done during a time of grief. By cutting the body, it let others know the extent of grief, and the cutting left scars for all to see. Again, the action was a means of drawing attention, not only at the time of grief, but for many years. It was a means of getting sympathy and enjoying man's attention instead of trusting God. Look at what the Baal priests did to get their god's attention when he did not respond to their prayers and Elijah mocked them for it. "And it came to pass at noon, that Elijah mocked them, and said, Cry aloud: for he is a god; either he is talking, or he is pursuing, or he is in a journey, or peradventure he sleepeth, and must be awaked. And they cried aloud, and cut themselves after their manner with knives and lancets, till the blood gushed out upon them." (1 Kings 18:27-28) By the way, their god still did not pay any attention to their blood letting, pain, or prayers.
As far as marking the body, it has the same motive as piercing and cutting. A tattoo draws attention of the wearer as well as others, is permanent, and changes what God created. Therefore, It can be said that tattooing is a strong statement against God's work in creating man. A tattoo says the wearer knows better than God and has turned from God's loving direction.
Yes, piercing, cutting, or marking the body for the purpose of changing it or to go beyond modesty in getting attention is sinful. God wants only good for us. He gave us His Law so that we could live well and prosper in His ways. Transgressing His Law only brings harm to us.