well it's a decent start. i'd crop the bottom third off of it, i'm pretty sure thats the blood splatter from the Akira cover, and the black box is a little to perfect, maybe take an eraser, change the brush to something and make it a little different.
Also yeah, the center is lacking... something. Maybe a little different shading would be good, and it won't be so bad if you make it a little thinner. The basic default sig is around 125 and 150 pixels tall and about 500 wide fits well also.