The first 8 are boring because they are literally cut out stocks placed over a partly black and transparent background. I consider that boring.
The 9th one just looks like 2 images placed together strategically...maybe. With text over them....yay.
The 10th one seems like more work was done, I don't exactly like it to much, but you seem to be actually doing something such as backgrounds etc...
This 11th one (orange) is not bad I actually like this one except for the way the clouds end off on the right.
The 12th one I'm just confused in...
I really didn't comment on any of the avatars. They're all pretty good.
As for the Death Note sig, it seems like you progressed since you made those first 10 and this one.
The last sig, is just weird. It's way to random and has absolutely no flow.