Firstly get rid of the enlarged render in the back. It throws off the whole thing, and just looks bad IMO. Its really random, and some brushing and lighting to give it some flow just to give a direction. Throw in some foreground effects as well to add some depth, as well as sharpen the render up as well. And change the text.
Not bad, It's not one of the best signatures I seen. But follow spitfire advice and it should help some.
First of all, it's kinda of monotonous pertaining to color. Throw away the enlarged render. Try to avoid doing things like that. Also take out the text or at least use a less sophisticated font, such as Arial. NEVER use a C4D as a background unless you manipulate it in some way to make it less...well, vibrant. It's not bad for some points, but try to work on others. You're getting there.