Noice, Few tings tho.
These are just personal opinions.
I dont'like signatures that big. It usually makes the signature kinda dull because it usually causes empty spaces, unless you put in alot of work to fill em in. In your case upper left corner, lower left corner and lower right corner are kinda empty(Yellow marked).
The signature is looking pretty flat. There is not really any depth. It's really dark, alot of details are dissapearing.
I personally don't really like the effect thingy i marked with blue.
I do like the part i markes with green.
It's got something going on with the background and had little bit of depth.
The black and white one looks a bit better.
but has the same problems.
Overall it's hard to do a ONE stock sig.
Nice try tho!