I have to agree with SAS:
Anything a short sleeve shirt and long trousers will not expose is fine probably.....just ask yourself if your boss would want you representing his company to clients.
and disagree with Hands on 123
but you always see pilots dressed in the "uniform" of black trousers, white shirt, gold bars etc,
I am the so-called "anti-pilot" when it comes to dress. When I flew in Hawaii, I wore shorts, aloha shirt and flew barefoot. I would often discuss with my pax (when they asked), about perceived professionalism. It mattters not what I wear but in how I carry myself and act. They were normally surprised to hear that I probably had more hours and experience than the airline pilots that flew them across the ocean.
These days I have discarded all such "pilot" identifying clothes and choose to blend with my fire crew---you will see me in nomex fire pants and shirt most days. It is actually fun listening to new ops people on a helibase trying to figure which one is the pilot.
BTW---I have a tattoo that is hidden by a short sleeve shirt---most people I work with do not even know I have one. Therefore, I would say it will not hinder you as long as you can hide it.