Getting tattooed is all the thing these days, including among Christians. The heritage of tattooing should weigh more heavily on the minds of such Christians than it appears to be doing. A more fundamental pagan activity can hardly be imagined (Lev. 19:27).
But the real problem with Christians getting tattooed has to do with the relationship of their tattoo to their baptism. All Christians are already marked, already tattooed, in their baptism. This is the mark of Christ on their bodies. So when a Christian heads down to the parlor, he is doing (consciously or not) one of two things. He is either trying to erase his baptism or he is trying to supplement it. He is trying to replace the mark of Christ or he is trying to improve the mark of Christ. But, of course, neither can be done.