As an old school Roman Catholic, I can tell you that tatoos - and piercings, for that matter - are regarded as "mutilation of the body," in direct contradiction to the proper regard of our corporal bodies as temporary houses of our souls and "temples of the Holy Spirit." Not sure how it's done today, but a reflection of this is seen in the practice of, in the event someone has a limb amputated, you have it properly buried, very ceremonially, with the rest of the body ultimately to join it in the grave. Orthodox Jews, too, practice this, and, if you're an Orthodox Jew and get a tatoo, you cannot be buried in the sanctified ground of an Orthodox Jewish cemetery.