-cracks knuckles- Okay here I go!
First one - The subject is too faded and my eyes go toward the brighter effect in the background. Your text is hard to read, it would be best to avoid text that is too code like to make it easier on other people to figure out who the sig belongs to. Also you should add some flow to the image. For example:
Make the background go the same direction as the subject.
Second one - Avoid covering the subject. Sometimes it's good to "wrap" effects around them but blatant plastering is really hard to look at.
Third one - The text is once again hard to read. If it wasn't for your forth one I wouldn't have noticed right away that it said something. Don't make it fade too much into the rest of the sig. The font choice itself could have been better. It looks like you took a sig off google and added words to it. Make it look like it belongs there.
Forth one - Same font notes apply here. Of course a little too bright for a forum with a white background. I can see it roaming about on a darker themed forum though.
Fifth one - I like the background and the subject. They match. The text however does not and ruins it a little. Try resizing it a little smaller. You want people to look at it and see the whole thing, not pause and go "Woa that font is gigantic. But the rest is really good."