Not a bad attempt at all..
The main problem i have with it is the render, it's extremely hard to see. The sig as a whole does not really have a focal point, if anything the text is because that's the lightest and easiest colour to see in the sig.
The text's font is OK, although the colour is wrong IMO. It should not be the lightest point of the sig.
If you created the background yourself, well done. It's a nice grunge effect.
The lighting on the guys shouders is quite nice, again, if you created that yourself.
Again, choose a better render, which is actually visible, or make it visible yourself.
Hope i helped.