In my opinion you should get a bit better modeling before putting them in a sig, either that or choose another image in the meantime.
And like was pointed out in a post above the model isnt very well cut out and that invert shadow dosent seem to be working out.
Not liking the sig itself either, too wide and those white-greyish spots on the middle and left look like you accidentally dropped paint drops on the sig.
Not sure about that font/color you are using either, but the placement isnt that bad.