One of the most important promises you make in your wedding ceremony is the promise to love one another forever.
When you illustrate ideas, like forever, you make them concrete and more understandable.
So: the more you can find concrete examples for a concept, the easier it is to make that concept reality.
The infinity circle is a well-known symbol for forever and it's easy to use in a wedding ceremony.

• Hand-fasting: A couple joins hands, right hand to right hand, and left to left.
  I think it's a much better image than a circle, where the overlap is complete.
  You remain individuals but are strongly connected.
  The power flows easily from one partner to the next.
  Isn't that what you want in a marriage?
• Inscribe in a ring: And then describe in the wedding ceremony.
  Years ago, everyone had their rings inscribed inside with at least their wedding date.
  But often they bore elaborate inscriptions -- quotations and assurances of love.
  The infinity symbol is a lovely one to have inside your ring which represents your marriage commitment and promises.
  Strong and enduring.
  That's what you want from your marriage.
  
• Mobius Wreaths: In many traditions wreaths of flowers or straw play a role in the wedding ceremony.
  Rather than a straightforward wreath, a simple twist of the flowers can turn your circle into a mobius wreath -- a wreath with no inside and no outside, which with one quick twist easily forms an infinity circle.
  

The more connections you make to the concrete world with your promises in your wedding ceremony, the greater your odds of successful marriage.
And the goal of every wedding ceremony is to create a life-long marriage.
In your wedding ceremony, metaphors are your friends and so is the infinity circle!