I'm not a fan of black and white signatures (and having the focal dead in the middle

). I'm not opposed to monochrome signatures in general but I need it to have some sort of color at least.
I feel its harder to get that special "zing" or whatever you want to call it with black & white, you know make the focal point pop out more.
However, that "effect" of having the picture fade to black like you did with this sig

is really cool and well executed. It fits that ominous feeling of the person in the sig, making him seem way more villainy than you could make him in a colored signature.
I also like this one a lot, really has great depth

The others are not bad either, it shows that you've spent some time getting good at black and white signatures. All of them seem carefully chosen in regards to the render and theme (which is probably not as easy as with colored signatures), so they really end up
fitting that black&white aesthetic.
Keep us posted