I personally think it should be their choice if they want it: Some tattoos have meaning and some are just there. My friends mom got a tattoo of a semicolon (info about it http://epicbh.org/blog/project-semic...iOIaAhjd8P8HAQ) for her depression in life. She also has tattoos of an anime cat which she had in representation to her cats. I know that went a little too off topic,but it sorta reflects people getting tattoos with different meanings.
Piercings are different it's more of a fashion choice which i personally don't like unless it's on the ears or lip, but what do i have to judge.