Three amazing contributions, courtesy of Ken Macklin himself:
These are scanned from 35mm slides he made prior to sending them off to Lucasfilm, and while the resolution is very high, the quality isn't the best. Still, the Eidolon scan will work as a great source for a complete version of the art.
The Maniac Mansion artworks are so weird, though, especially since Ken stated these were commissioned by Lucasfilm AFTER he had already done the MM key artwork. Why further art uses these strange characters is unclear.
Also in the works: Based on the original oil painting Steve showed in his recent interview with Daniel, I've decided to create a more muted version of his MI2 artwork, trying to emulate the softer look of the original. This still needs some work, especially in the now brighter dark areas, where some of my touch-ups became more apparent.