The controversy surrounding this subject of whether a christian should wear tattoo or not has been raging on for far too long now. It is something that, for me, shouldn't have been something taking this extent, because there are so many scriptural passages to seal thing off on the matter.
Basically, as christians, we are taught not to conform to the things of this world, but we are to transformed by the renewal of minds, so that we can prove that which is good in the sight of our God. Tattoo is this case, is seen as a worldly thing, which God is not pleased with because it defiles His statutes.
A notable statute that prove tattoo is bad to be worn as a christian is that the Bible made us to understand that our body is the holy temple of our God. And that we are made in His image and likeness. If we are to go by these statutes, since God himself wouldn't engage in tattoo, it won't be appropriate for any christian to do so.