some people like to see in this challenge only reflective (mirror) symmetry. They take seriously the challenge description specifying that "the same photo should be flipped to artificially create a symmetrical image". It should be noted that rotational symmetry as shown here can be achieved by flipping twice.
Post challenge:
I made an improved version, which would not pass validation any better:
disqualified for adding text, but if you'd drawn or photographed an s onto a picture file and then included it? all water under the bridge, of course...
Cute idea and well done, but not symmetrical at all (as I'm sure you've heard many times by now)
Had to give this a 1 for DNMC. Normally I would -3 but since in this case, the theme was a hard and fast rule totally within the control of the photographer, I'm forced to be a little more harsh.
Upon reflection, this is an example of rotational symmetry, so I take back the DNMC and score this for the image itself. Well, done! a 7