IF you are talking about using the "Share" icon from within the new "Photos" app and choosing "Mail" as the means by which you intend to share the image, then.......
The contacts are pulled by the "Mail" app, from the "People" app and you can bring up your list of contacts by clicking the little Head & Shoulder icon in the "To" text box, right side next to the "Bcc / Cc" links.
The Mail and People apps are inter-connected.
IF that is not what you are asking then you'll need to clarify, just what it is you are attempting to accomplish.