See, personally, I'm not bothered by tattoos. It's a personal choice. Someone once said that the only difference between people with tattoos and people without them, is that people with them don't care that the people without them don't have them. If you want to put art on your body, I don't care. It's not affecting me.
On the Christianity note, I was taught not to judge other people based on their appearances. Only God can judge me. Not one of us on this forum is God. So what grants us the right to pass judgement on what people want to do to their bodies? For some people, it is a religious act(as not everyone is Christian, and we should open our minds to that fact). You can worship your God(Gods, or Goddess, as the case may be) and I'll worship mine. Mine tells me not to judge other people on their appearance, and that I should concern myself more with being a good person and doing good things. Whether I put art on my body or not, does not affect whether or not I am a good person.
:]