This sig is pretty good for it being your first. I like the minimalistic style of it.
Compositionally i think it would be more pleasing if you scooted the render over to the left about 10-15 pixels (maybe about your thumbnail's length over).
The coloring is okay, it blends with his skin tones pretty well, however i don't know if i would have picked that to be my main color. IMo i would have gone with the armor, like a nice gray blue.

The blending is pretty good, though I'm having a hard time seeing the render because he seems like a little soft or something. A way to fix this is to duplicate the render layer. Move him to the top of the layers pallet and then erase the sides.

As said before, stick to default fonts it will help you work wonders. I reccomend you read a few signature tutorials. I highly recommend mine, daemon's and ilovecoheed's.

Also you should read this:
Darkmethod'S guide to text

it'll help you with your text a lot.