It's not a bad sig, just a few qualms I have with it. For one the purpose of pop out sigs is to give the illusion that your render is coming out of your tag/canvas. so when effects outside of the said canvas areas are abruptly stopped; like here.
*
lol you split your piece into two parts so I had to printscreen for ease.*

You're killing the illusion. So I would take a soft brush on low opacity and erase some of those areas and take your pentool and round off that object on his back.
1. Make your shape with pentool set on "Paths"
2. Right click> make selection
3. Hit delete.
So you should end up with something more smoother like this.

Clean up the "sloppy-ness" on the right side and you should be good to go. Personal note I don't think that motion blur is all that appealing in the current version you are using but meh. that's your call.

Hope you don't mind I went so in depth and offended that I used visual aid. It's not that bad I'm just bored. Other then that I got nothing more to say so I'll end it with nice work you're and you're definitely on the right path. "9/10!!" =}