This is more or less the first time I've tried to make sigs. I've really only busied myself
with my website layouts before, but I thought I might as well try to make a few.
1st one is kind of plain, unatractive, and the color is bleh./
second is better but the extrude filter you used does not look very grand in the sig.try some colors.
For first time, its a good start, dont take me harshly.
Practice tutorials and you could get good in no time.
You have potential.
For first time its pretty good, but in the second one the render of the girl doesnt work to well. Renders of people just standing with a blank stare never do good in signatures.
The top one is good, but like Atomica said, try changing the color and stuff. Very good for your first time though