Nice idea but it has been done before and a bit better IMHO For me it is distracting that the white line doesn't ends in the point of your brush and a white line coming from a black brush is also weird. However I have to say that overall it was a good attempt. keep working hard on your skills!
another homage shot to the original light painting image - but the issue I see is that the 'paint' seen under the brush - shouldn't it stop right where the brush is?