Some Christians argue against body piercing and tattoos on the basis of a couple of Old Testament verses that prohibit them (Lev. 19:28). Several years back an aggravated lady tried to get me to preach against these things in my church (she’d observed that a number of people in the congregation had body piercings and tattoos). I brought an end to the discussion by pointing out that her ears were pierced and she was wearing make-up. She apparently hadn’t noticed the contradiction.
If we’re going to go to the Old Testament to determine what we can and cannot do, then we better be prepared to forbid wearing wool and cotton together, because the Old Testament is also against this (and several hundred other odd things). Body piercing and tattooing were forbidden in the Old Testament because they were associated with pagan religious practices. They have no such associations today, so these passages don’t apply to us. On this and many other matters, each person has to follow their own conscience (see Rom. 14).
Of course, we who have pledged our total allegiance to the Kingdom of God need to realize that we’re God’s advertisement to those around us. Our lives are to reflect his loving character. So we should be careful about what we’re advertising with our body piercings and our tattoos – as well as with our clothing, our activity, and everything else. But there’s nothing intrinsically wrong with decorating one’s body by piercing it (as with earrings) or by putting on tattoos (or make up).