Another aspect could be summed up by this familiar quote from a children's story. Whether talking about all tatoos in general, or a very specific image on a single person. Just substitute "tattoo" for "word":
"When I use a word,' Humpty Dumpty said in rather a scornful tone, 'it means just what I choose it to mean — neither more nor less." "The question is," said Alice, "whether you can make words mean so many different things."
Where HumptyDumpty is the tattoo wearer displaying something with a specific meaning in mind. But everyone else receives a different message with different meanings.