Or a willingness to simply ignore the biblical prohibition under the law. I acknowledge that Christians have liberty in Christ and are not bound to observe the law, but a large swath of professing Christianity still believes that they remain obliged to obey the law and try to divide it into moral code and ritual code. Since they have no clear dividing line between the two, why should I use my liberty to cause the spiritually weak to stumble, all for the sake of vanity?
A tattoo might open a door to conversation and even make a listener more comfortable, but it isn't necessary to have one to share the gospel or to find common ground. People share common experiences in all the common matters of life.
If you have a child, you don't need a tattoo to have a friendly conversation with a tattooed mother or father. People share common issues of family, of vocation, of political orientation, but more significantly of trials, of sicknesses, of personal loss.
A real testimony is about how Jesus has saved, has guided, has helped, has comforted, has taught, has served, has loved us and changed our lives, not how we've gotten a tattoo, or a choice of a car, or a taste in music, etc.
We have liberty in Christ, but our testimony is less about delivering the gospel than about how the gospel delivered us.