A design request by a post-doc in comparative religion; he wanted something to reflect the focus of his dissertation: the concepts of eternity and chaos. This design is also found in the publication of his dissertation.
Edit: I get a lot of questions about using this particular design. It was a custom design specifically created for someone - it has been inked and is not available for public use. [link]
However, the basic concept of the eternity serpent (ouroboros) in a figure eight is an ancient image and not my unique creation, so if this inspires you to create your own distinctly different rendition, then feel free.