If it were a customer service job, I would want them to cover them up as much as possible. If it weren't customer service, I would have no problem with it. I don't think tattoos have any effect on their work ethic.
For most customer service jobs I think they are inappropriate. The only exception I can think of off-hand would be an out-call "massage-therapist" I suppose a tattoo of a picture frame on her spine that read, "insert picture here" would enhance customer satisfaction