The light is nice, shadow works for me, but the sketch looking away and the static wheels on the scooter and angle of the rider makes it look like he's about to fall over.
Using the sketch on the other side of the scooter might have been cool...almost like even the picture is turning to look at the new scooter.
Need some sense of motion on the scooter/wheels, in my opinion.
To get the motion, you could have used aperture priority mode so as to use a larger aperture with the flash. Second-curtain sync would put the sharp part of the photo (the frozen part) up front.
If you moved to manual mode, along with the larger aperture, the longer shutter speed would have worked together to capture even more of the ambient light - and the motion.
The additional shutter speed alone will not get you enough ambient light with the flash, as you found out.
Great idea - and you nearly pulled it off! (I like it anyway!)
If the image was for publication (as indicated in the OP) it would be a gross violation of photojournalistic ethics to clone irises or add motion in photoshop.
