German law prior to 1965 protected works for the life of the creator plus 80 years; as Gutschmidt died in 1926, his works would have entered the public domain in 2006.
I would assume Richard O'Brien still holds the copyright.
It's hard to say because the ownership in the magazines he worked for were sold off or fell into abeyance. Several years ago an article with many original illustrations and reproductions of magazine covers was published in an art magazine, and the contents of that article were copyrighted by the author, so it may be that those images are under copyright.
Depending on the agreements made in commissioning his illustrations, they may remain his intellectual property or may transfer to the publisher. Mr. Innocenti may be contacted through his agent: Jonathan Cape, 20 Vauxhall Bridge Rd., London SW1V 2SA, England.
Unless other arrangements were made, the creator is the initial copyright holder.
Warner-Tamerlane.
Muppets, Inc.
Unless other arrangements were made, the creator is the initial copyright holder.
Little, Brown.
Catchme.com is registered to Slingshot Labs.
The Rank Organization.
The Richmond Organization.
You would have to have the permission of the artist or company that holds the copyright on the artwork.