When I first look at the piece, my eyes go directly to his face. But when I take a closer look, I see that there is no focal at all.
The render you used was going to be your focal if I'm correct.
You tried to do it by adding lightning and a little bit of sharpen and blur, but it didn't execute that well.
My tip would be a better background, as this one is too negative.
Blur it in layers, so make it that layer 5 has 100% blur, layer 4 80% blur, etc etc. Then layer 1 sharpened and stuff, if you get what I mean?
Depth isn't all about blur and sharpen, you gotta look out for lightning also.
If you look at the render that you've used, you can see where the lightning should be coming from, yet, you did it wrong.
The lightning should be coming from the upper right to the middle left, but his right shoulder is very bright, and the rest isn't.
Create a new layer, fill it with black, set it to linear dodge, get a 300px soft white brush, and mess around with it. Don't over do it though
The background is kinda empty and way too negative. Go for a darker and sinister background the next time, and don't do smudge, as a smudged background won't execute properly that often.
The text is kind of distracting, as it is very pixelated.
It doesn't fit in with the rest of the signature, and it's in the wrong place.
Try to go for a textless version ( a ''tag'' ), or look up some tutorials about how to make your text perfect.
And last but not least, don't do B&W, as it often ruins your piece.
I didn't really understand is depth concept. I usually just blur it at the maximum blur that I want. Then I get like a 10% opacity eraser and just erase what needs to be erased going over parts several times to get them at the right opacity.