Theme trends for tattoos

I'm doing some research for an article, so personal opinions as well as observations would be greatly appreciated. When it comes to tattoos with a spiritual bend (mandalas, totems, lotuses, kanji, hanzi, crosses, saints, etc.), what do you think is the motivating factor? Why do people want Buddhas and prayers and such on their skin? As an "bonus question", what do you think is becoming the most popular spiritually-themed tattoo motif and why?