At any tattoo parlor, one is likely to find an artist who is willing to tattoo an image from the Wizard of Oz. The tattoo artists can recommend different Wizard of Oz designs for different parts of the body.
First choose the type of Wizard of Oz tattoo. You may want to identify a particular character, such as Dorothy or Toto, and then do a sample sketch and show the tattoo artist the image. Print out a screen shot from the Internet, and take it to the tattoo artist for inspiration. A tattoo artists can sketch over an image, transfer it to a wax paper and produce a rough idea of what it looks like and its actual size.