This is a very good idea; it combines the rock with both paper and scissors in a meaningful scene. But the image itself is not as strong as it could be. I'd like to see more of the kid's face and more of what he is doing. I also think the wave is distracting. Maybe a vertical shot from a lower viewpoint to the left would be better.
I think this picture succeeds very well in meeting the challenge. From a technical standpoint, I wish there was a bit more room above the child's head. Otherwise the focus and exposure is quite good and fine detail is preserved well.
I believe the photo is too tight top and bottom. It would have been nice to have all of the childs head and feet. Other than that I think this is a fine photo.