Off the cuff, my initial reaction is to say that I'd have Federico do ALL of them, but since that's kinda cheating and dodging the larger implications of the question, I'll break it down like this:

The Visitor Sketches: Mike Mignola
Most people know Mignola's incredible work from his Hellboy series, but I'm basing this choice on the DC Elseworlds one-shot Batman: Gotham by Gaslight. Most people may not realize that there is, in fact, a loose narrative behind the album, detailing the exploits of a dying king and a mysterious stranger who enters his court. Mignola's style would add a lot of weight to the darkness of the content and the obscure, semi-occult referencing.

Freestyle Fondue: Gabriel Ba
This album is kind of the black sheep of my discography, since it's so jazzy and laid-back. When I picture an illustrated version, the fluid lines and bright, retro colors of Gabriel Ba's work on Casanova come to mind.

Quanny Sitar: Frank Quitely
Frank Quitely's stuff is just visionary: his artwork is beautifully detailed, and he tends to favor bright, eye-popping colors. Consider his work on All-Star Superman; now, imagine if All-Star Superman was an illustrated version of a psychedelic Indian gangster epic starring Amitabh Bachchan and Zeenat Aman.

Beyond All Spheres: Federico Piatti
Need I say more? The Beyond All Spheres cover art was basically this. It already happened. I'd love to work with Federico again, though; there have been brief discussions in the past about short-form comics that would accompany album downloads...

Sigils: Ben Templesmith
Templesmith is one of my favorite artists working right now. His style is utterly his own, and a lot of his work touches upon the occult, so I think he would be the perfect man for the job on Sigils (see Wormwood: Gentleman Corpse).

After scanning my unconscious mind, I believe the three forms the AI would be most likely to choose include Carl Sagan, Christopher Walken and The Dude from The Big Lebowski, all with an equal distribution of chance. So no matter what, my new ancient starship will be totally effing awesome.