I look at tattoos with the attitude Paul had concerning many things. To the pure all things are pure. And also, if what I do in my liberty offends one of my brothers, then for the sake of conscience of the weaker brother I will abstain. Is is all about our neighbors and living peacefully with love and consideration of others within the body of Christ. This is a forgotten lesson and many abuse the liberty we have in Christ and so offend many.
Not just the act being a sin, but causing others to stumble is even worse, as Scripture says clearly.