Not bad for a beginner, heres what i would say to work on: 1. Colors, the colors you have are boring and lackluster try to spice em up. 2. Render blending, right now it sticks out a little too much. 3. Text and border, kill the border all together or keep it simple is usually the best way to go. As for text keep it simple, and try to use minimal effects on it so that it doesn't draw away from the focal. That's my advice for now, keep it up!
I agree with everything said there. Also, you can see how you duplicated and spatter the render on the bg behind your main render. That isnt bad, and its a great technique if your going for a grunge look, but on the left side you can still see the face of one of the duplicate renders, not that well, but it kinda ruins it. I know it sounds knit picky but its all about the flow man. Other than that, its not a bad sig. Keep it up bud!
Haven't seen your stuff before, but you're definitely not bad for a beginner. I think you've got lots of potential. Just keep workin' on tuts to learn new techniques and keep getting CnC bro. Work on your text, Inverse has a great tut for that in the graphics tut section.
The sig would be nice without the border and the text. Use simple fonts for tags. Take a look at the tags made by the professionals in this forum, and you will see that the font they use are actually fonts that are rather simple and neat. (What I would like to call 'modern fonts'. Eg. Century Gothic) The lighting on the top of that sig also doesn't really serve much of a purpose. Also, keep the border simple. Or don't put one at all ^_^ Keep it up!