How do you become a great artist? Or even just a good one? With practice. Lots and lots of practice.
That's a problem for tattoo artists. Not many people want to be an inker's sketchbook. That's why Tattoo Art Magazine invented the SkinBook. It's a book filled with sheets of a synthetic product that behaves like human skin. The pages are photographs of human body parts that are commonly tattooed. This permits artists to get a sense of what a design will look like when applied to an actual human body.
-via Lost at E Minor