The size of the tattoo is an important factor which shall help you decide the place of your tattoo, like big designs are best suited at back whereas small tattoos can be done on arms, neck and feet.
Another important thing to consider is its visibility, i.e. do you want your tattoo to be visible by others. In case if you want it to keep it as a secret then places which are hidden on our body shall be chosen for the tattoo, but what if you want to flaunt your tattoo then you choose areas like arms, shoulders, neck etc.
Tattoo can be done anywhere except hair, toes, nails and teeth.
You can choose your head to get the batman tattoo, provided you will have to shave off your hair on the tattoo, and if you want to hide it in future then growing of hair shall help you out in that case.