I just went in and messed with some of the some of the stuff I learned. C&C always welcome

Nice color and background, it all goes together.

But the guys face in the middle looks pasted in, and the font doesn't fit well with the design exactly.

Yeah the render I used didn't allow for much. I reworked it with another render and got this:

Loose the lens flare, please. There are much better ways to do lighting. It can be effectively used for other things, but as a stand-alone light source, the lens flare fails.
The green border around everything is pretty gross too. It stands out from the background so much that it is really distracting.
One thing that might help you, is to not make your signatures as big as you do. With the two you made, the render doesn't take up hardly any space in the sig, and then there's all this empty space with not much there. Empty space can be used effectively, but it's a little harder to do, and these just aren't doing it for me.
I think you'd benefit from learning how to blend all the parts together a little better. The way it is now, you learned how to do the background and the border, then you stuck the render, text, and lighting on it, and they just don't fit. Instead, find a tutorial, or just try some stuff on your own that incorporates all the parts of the sig together, so that everything blends. Make it look like your render belongs there and wasn't just stuck there. It'd really improve your sigs a lot.