Just rememeber if you want the snake to be realistic, the artist is going to have to draw it pretty large to get in all the details. I have a snake on my back, it's pretty big but I had him make it kind of animated looking in a way.. because I wouldn't have been able to afford what he had in mind and what I really wanted.
Mine cost $340
I would show you an updated pic of it, but its on my lower back and its very difficult to take a picture of your own butt =P