Do NOT be impressed by the flash on the wall. These illustrations are usually purchased from other artists and do not represent the work of your artist. Frankly, anyone with some experience can easily trace the outlines of these illustrations and fill in the colors. What you really need to look at is a book that contains a collection of photos of the artist's work. Go to the counter and ask to see one. If they tell you they don't have one, walk out immediately. You're visiting the shop to commission a piece of art to be permanently illustrated on your skin; for the artist to tell you s/he doesn't have samples in a portfolio is insulting.