Not bad for a novice though there's definately a lot of space for improvement.
For the first signature, I don't like the glow around the render it doesn't fit with the whole signature. I also suggest you blending the render in with the BG so that they have a flow in them. Text is okay, but I really don't like the animation around the pixel text, it's really disturbing and makes me lose my concentration on other parts of the work. Not sure about that cross thing at the back of the other text, looks weird imo. Not too fond of the border either but nice job on that one.
As for the second signature, the text kinda ruins the whole signature, one it's too big and two I don't like the bevel and emboss effect, I think it looks rather, out of place in this case. Render is okay, but it would be nicer if you use the render as an advantage to fill out more of the signature space instead of pushing it right to the side. All the bland space makes the signature look really dull. Also, the lighting isn't really correct though it doesn't really matter at your stage yet imho. Maybe a little bit more depth on the BG, up to you.
Good job though, keep trying, read some tutorials and experiment around, I'm sure you'll come up with a style that you like and looks good. Keep it up :)