Nicely done, good involved piece and has the 'painted' finish to it that I like, detailed and actually interesting to look at. The color itself flows, with enough contrast and highlight to draw your eye into it, but I think, it's slightly over sharpened mostly noticable around the white area to the right.
Again, the high standard of that sig is let down by such a simple use of text and font work. I'm really disliking the use of that line as well - the whole design would benefit from some sort of techno-styled font to help complement and tie it together better. As I've already commented before else where, text-font work is part of the design process, as it stands it looks like the last thing you did, an after thought - tbh average and it could easily be improved.
Other than that, great work and well brought together.