Ok its a good sig, probably the best effects you have made imo.
First, try to avoid FHS (Floating Head Syndrome) So the head is only showing, just try to have effects on his shoulders + chest and something, but dont cover up the his body

(not saying that it is in your sig, just a tip)
Those big glowing circles..maybe a bit too much of them..taking most focal away with that glowing pieces.
The render: You gotta make the render cover more of the sig.. there is too much empty space that is just not being used (left side of the sig) really nice effects on his shoulders, love it.
I needs depth..(not saying its really neccesairy in sigs) but it would look better with some depth..find a good background, blur it a little,place the render and make those effects like you did in this sig, and it would look alot better.
Lighting: It really needs a light source (main) like i said those glowing circles kinda take the balance off the lighting,but it looks good.
Needs text

and try to have the border 1px, seems like its 2px
BUT overall, it looks good, your getting better <33