Txt = Text
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Pretty good for a beginner, but there is a lot of room for improvements.
#1: Render is too small, makes the overall signature look boring because there isn't much to cover up or make it look interesting. And I think you overblended the render too much.
This is the one mistake most beginners make, making lots of text and making them huge to cover up most of the BG. I also suggest taking the "Bevel and Emboss" effect of the text, as the might look better.

#2: Can't see that one..it says "User posted image" for me.

#3: I like this one the best out of all the others. Nice effects and BG, not as boring as the first one and more depth. For now, I would say work on your text placement and lose the outerglow on the "Got Sig?" text. Really nice though.

#4: The same comment I made about the text on the first signature, but this one's better because it's not as monotoned and the render is blended way better.

Read some more tutorials to help you and guide you around, just don't forger to experiment some filters yourself. Good work though, nice job for a beginner