If parts of the body are cut off, you don't want to put them into the middle of the sig, unless you blur/smudge them enough that it looks like the rest of the body is behind something.
you need to choose better images to work with.. choosing images of a guy missing an arm and a half arent doing it. go to planetrenders.net and browse their renders.
you need to spend more time on a single signature than making 10 different ones.. quality, not quantity and im sorry but the only way your going to get better is with tutorials & practice, this doesnt happen over night.
1. The render should look like it belongs in the picture... ie. you can't just slap it on anything and blend a duplicated layer behind it.
2. Try using a regular text like arial, comic sans, or verdana... the more complicated your text is the more cluttered your sig is going to look...
3. You can't improve if you don't take the advice people give you... doing the same things over and over are not going to make you better, it's actually a sign of insanity to repeat the same procedure expecting different results... just sayin'