Whenever discussing IP issues, please make a very clear distinction between copyrights, trademarks and patents. They are entirely different things.
Copyright only concerns complete creative productions like books or illustrations, and only their exact form or direct derivatives (like translations, variants or long extracts). Whole HPL stories were under copyright but most likely they aren't any more. Many works by other authors still are. Also, later discovered and published HPL works may remain under copyright. What's important is that a single word like "Cthulhu" or a rough likeness of a squid-headed creature cannot have a copyright, thus the whole point of expiration is moot when it comes to sculpting your own Cthulhu mini or writing a new mythos story where Cthulhu appears.
However, terms can be trademarked, regardless of whether you were the original creator or not. Furthermore, trademarks only apply in a certain context. Therefore Microsoft may have a trademark on "Windows" in the context of computer operating systems. They didn't invent that word, and it has zero relevance for selling your glass products as "windows" or "Bob's Windows". Apple Records has a trademark on Apple brand products in music, Apple Inc has it on computers. They've repeatedly got into trouble with each other regarding online music sales, but hardly with fruit vendors.
Trademarks can expire quite easily if you don't use and protect them. As GW and MB didn't print or support HeroQuest for decades, the brand expired and now Issaries uses it for their Glorantha RPG. Meanwhile, MB probably still has every bit of
copyright on the boardgame graphics, rules text etc.
So if you're selling Cthulhu-branded stuff, the only relevant part is whether there's a trademark on Cthulhu in the context of games, toys or model kits. I checked USPTO for "Cthulhu" and found:
- "Cthulhu for President" (Chaosium Inc.), "books and games", abandoned in 2006, dead
- "The Cthulhu Cult Collector's Edition" (Visceral Pictures), discs, cassettes etc, abandoned in 2009, dead
- "Call of Cthulhu" (Chaosium Inc.), "rules book and supplements for playing a fantasy RPG", renewed, live
- "Call of Cthulhu" (Chaosium Inc.), "equipment such as rule books, world map, and cardstock playing figures sold as a unit for playing a role-playing game set in the 1920s", cancelled in 1990, dead
So only the current incarnation of CoC by Chaosium is active, and it only covers RPG material. You can happily sell other stuff under a Cthulhu brand, but I guess people are avoiding it in the contect of RPG-like games due to:
1) respect to Chaosium (sort of gentlemen's agreement)
2) preventing clashes, because it would harm such small companies far too much
3) creating their own brands instead.
Note that this example was for US trademarks only. It gets more complicated worldwide.
Anyway, HPL himself actively advocated the idea of propagating mythos names and creatures over other authors' works. It's completely against the original atmosphere to claim ownership of the terms or descriptions. Still, it would be nice only to use the original concepts as building blocks for something new with your own twist.
Finally, if you're basing your sculpt on any particular, copyrighted piece of illustration so closely that it counts as a derivative work, it doesn't matter a bit whether you call it "Cthulhu", "not-Cthulhu" or "Shirley" regarding the
copyright issue. If you're violating a
trademark, adding "not" to the name is unlikely to help either. It looks utterly stupid too so could we just get rid of that already?
(Disclaimer: totally not a lawyer, but trying to get at least closer to the truth on IP issues.)