Batman makes an amazing tattoo. If it is an old school Batman, it looks great with the older style blue/grey uniform in place. If it is a newer style Batman, the tattoo can look amazing in black and grey because of the "dark" style, hence the "Dark Knight". Be original as possible.
Many people love the Christmas season so much that they get tattoos inspired by the holiday. I have seen everything from Santa, snow, The Grinch and more. Men and woman have gotten these awesome tattoos. Just try and be original. Get a good artist to do it.