I made an older version of this design about a year ago or more. I've always wanted to have it made as a shirt but I thought Threadless had limitations on the # of colors you can use. But, I just noticed that is no longer the case, so I finally just touched up the perimeter of it to make it a complete circle and am finally submitting! :)
You can see entire image here: http://gensanity.deviantart.com/art/Element-Expanded-434146281?ga_submit_new=10%253A1392423480
You know you want it.