Like Jarett said, it comes down to the guy. Especially with body art, which is very subjective even to people who do like it. I mean, just because I *can* be attracted to a woman with tattoos, if they are in poor taste or badly done, it would probably be the opposite; the same for piercings.
For example, I kind of find "tramp stamp" tattoos repetitive and unoriginal. They hardly ever convey any kind of creativity and while it doesn't make me less attracted to a girl (providing it isn't a _horrible_ tramp stamp) it certainly doesn't make her more appealing. An example of an exception would be this:
link That is an excellent tramp stamp, IMO.
Also, I think something like this:
link is absolutely gorgeous. It's great when you can get a tattoo that accentuates your body's curves and actually adds depth and sex appeal, by the art alone.
As for piercings, I'm fine with anything from none to moderate. My limit would be, like Jarett said, "a bunch of metal in your face". That has passed the point of moderation.
I'd say moderation sums up my opinion.