Well, it doesn't look like you did too much to the stock. I think that the colors look a bit odd... the color of the gargoyle doesn't really match the light sky blue background (I know that it looked like that in the stock). The motion-blur is pretty cool. I can't really decide whether or not I like the text... the border is a tad thin as well. Really, the only issue is that there aren't many effects. Its an ok sig, but I think you should add more effects.
I actaully did a crap ton to the stock lol... but they don't show as well cause then I did that motionblur. But at the same time, I like the more simple look. And I don't really like thicker borders, but maybe I'll try a 5px one or something and see how that looks. I also felt like any C4Ds I added just didn't work well with it... couldn't find one that I liked that looked well, so I didn't use more than maybe one or two in there. :/