I once read this novel with a girl having tattoos on her shoulder, chest etc. There also was a tattoo artist and one day a guy walks in romance starts, but I forgot if it included vampires or demons but something was there.
It was part of a series.
Not much to go on here, but this sounds a little like Rain Dance (now retitled as Soul Storm) by D.N. Erikson. The protagonist has a magical tatoo on one arm (just a light show, but not everyone knows that) and makes a living by reaping the souls of the dead for her boss, a vampire two thousand years old.
There is a tattoo artist, the one who put the tat on her arm, and his son (a good-for-nothing sort), a "dwarf Jotun", only about eight feet tall, a werewolf assassin who tries to kill her near the beginning, a human FBI agent with a magical tatoo of his own and a romantic attraction for the protagonist, and of course the rain goddess who brought her back from the dead.
The book is the first of a series; at least three are available now.