by Peter Ward in the book Drawn In: A Peek into the Inspiring Sketchbooks of 44 Fine Artists, Illustrators, Graphic Designers, and Cartoonists by Julia Rothman
Close up skull would be a good tattoo, with something hidden in the eye. city scape, comic book scenario/villain, doctor who reference etc. Thigh/side/leg/upper right arm (ribs maybe? but PAINFUL)