io9 caught up with artist Jeffrey Henderson who offered the following about Sam Raimi's cancelled Spider-Man 4:
Bruce Campbell would have been in Spider-Man 4 in a cameo role as Mysterio that would have been a part of the beginning of the film featuring “a montage of C and D- list villains that we knew would never be used as main antagonists: Mysterio, the Shocker, the Prowler, the old school-onesie-wearing version of the Rhino, maybe even the Stilt Man, etc.”
Vulture would have been the main villain: "The thing we kept coming back to was that, as a character, everyone was going to dismiss the Vulture as just an old guy in a silly green suit,” Henderson said. “So we wanted to go the opposite way and really make him the most fearsome and formidable adversary that Spider-Man had faced in the series.”
You can check out the Spider-Man 4 art up at Henderson's site.
As a bonus, here is video featuring Toby Maguire talking about Spider-Man 4 days before it got cancelled: