The beauty of massage therapy: it's where art meets science. MT's tend to rock their own distinct styles, anyway. Clients don't expect us to be wearing business casual, as long as your demeanor is professional and you're knowledgeable about what you do. One MT I know got the logo of a client's company tattooed on the back of his hand, because the client paid him $1000 to do it. Did it ruin his business? No.
Make sure it's not something obscene, which actually would be a problem for you, and you'll be fine.