The first is Ken Macklin, who designed the cover for Maniac Mansion. He will be doing the cover for Thimbleweed Park as well.
The second is the creator of Zak McKracken, David Fox. He worked on Maniac Mansion as well, doing most of the SCUMM scripting for the game, and is apparently the one we have to thank for the hamster in the microwave joke.
So if you haven't backed yet, or want to move up a pledge tier, now's the perfect time to head over to the kickstarter and back the game.