This photo appears too dark to me. While I can tell that the STOP sign is there, it is overshadowed by the darkness in the shot. Good attempt, however - challenge theme is definately captured here.
I think there is some room for improvement on this shot. I would recommend not using backlighting for this shot. All of the colors are washed out- you can barely tell that the grass and trees are green. Alternatively, full backlighting and underexposure so that you are only capturing a dark silohuette may work as well. The pole at the right should be cropped out of the frame. If the stop sign is intended to be the main point of interest, I would tighten the composition on it. The background for this shot is not very interesting and doesn't really need to be in the shot.