I offered to tip my artist when he finished my latest tattoo on Friday and he did not accept my tip. I think it definitely is a bit different in Australia, tipping often becomes awkward except when paying for a meal.
I think I tipped about $100 for my first tattoo, not really knowing what was an appropriate amount.
My theory is offer a tip or a gift and if they don't accept it no problem at all, and if they do, that's fine as well.