Eh, Sorry but I don't like the first two, my idea of a good sig is polar opposite to what your's look like. The last two though are quite intresting.

Quick rating.

#1: Horrible - Blurry, bad background, too dark.

#2: Decent - Not so good blending, + I dont like cartoons or whatever that is.

And the last two.

#3: Very good render, you did not lose any quality while cutting. Very good job. Only thing I wouldve done different is tried to get brighter render. 7/10

#4: NICE! Good everything, this is more of what I want to see! Keep it up! 8.2/10

Notes: I noticed that your name was not one one of those sigs, Im assuming they were from other forums but other people may not be so reluctant to beleive that you ripped those.