Synth's sig is blurry because of what he wanted to portray - a sense of speed. Motion blur is perfect for that.
As for your sig, I agree with Spunky. Why don't you try making a much smaller signature and pay more attention to the details in it, than making a big one that looks empty? I have the feeling that there's too many shades of green in there too, the dragon-like effect surrounding the stock looks really off compared to the background. The background itself is more of the same, and it would look better if it would be more diverse.
Hope I've helped.