You suffered from your image being too small. Take advantage of the full 640 pixel length for all your photos on DPC. As for the photo looks to be a fine shot for the negative challenge...maybe a closer crop would have also helped it score a bit better though...give more detail to the rider.
This image is really too small but it appears quite soft. Also, I think it would be better to have the right facing figure closer to the right edge of the frame so s/he is facing into the frame.