I've never really understood tattoos, nor had much interest to them.
As I understand it though, tattoos are often personal things that symbolise something of significance to the wearer.
In the context of Buddhist tattoos, there will obviously be some reaction... it is that reaction which, as you say could be a "help" (if it promotes mindstates of wisdom, lovingkindess, generosity) or a "hindrance" (if it promotes mindstates of delusion, greed or aversion).
Each person's reaction to their own tattoos will be different... if you're contemplating it, think about how you think you'll relate to it.
"Do not force others, including children, by any means whatsoever, to adopt your views, whether by authority, threat, money, propaganda, or even education." - Ven. Thich Nhat Hanh
"Whether I were to preach in brief, Sāriputta, or whether I were to preach in detail, Sāriputta, or whether I were to preach both in brief or in detail, Sāriputta, rare are those who understand." (A I 333, Sāriputtasutta)