I don't like his spot.
Also, if he's a biker why isn't he wearing shades and a German WWII helmet?
I'd take one of those classic 60s/70s images, bump it around with Gimp for a bit, then apply a cartoon filter to it, stick with a red/monochrome look and make the small text jaggier.
"plus, he doesn't look very brutal, more wistful. "
Like he's wondering why his grandkids don't visit as often as they used to. I'll tell you why - that spot.
Ah, here we go:
http://www.itsdeadlicious.com/2008/1...h-library.html
Obviously, in the spirit of classic exploitation fiction, the cover should reveal a scene that never occurs within the pages of the book. May I suggest a biker launching across the raised Tower Bridge as a scantily clad pillion passenger (preferably female, but go nuts) clings on for dear life on the back of his Bonnie, while zombies swarm underneath. In dinghies.