Follow the movement
The curve of a snake can guide the eye around a flower or through a larger piece. Compare a vertical composition with a circular one to find a shape you like.
Balance dark and open areas
A dark snake against an open flower creates contrast. A lighter snake with a shaded bloom changes the focal point. Collect examples of both approaches for your artist.
Ask for an original interpretation
Use reference images to explain the movement, texture and mood you want. Your artist can create a drawing that fits the intended placement without copying an existing tattoo.