That Seal of R'lyeh story I can totally picture as a 70s flick with a muscle car/penis-mobile driven by the main character wearing slightly "hip" New England preppy fashion, lava lamps and ceiling mirrors in his bachelor's pad, a round bed, the whole nine yards.
Strangely enough, there was a kind of trend in the '60s - early '70s towards adapting (read: ripping off) Lovecraft. There was "The Dunwich Horror" and "The Haunted Palace" of course, but there were lots of little ways Lovecraft was worked into flims, too. Fer instance, a famously awful movie called "The Touch of Satan" rips off some lines from "The Horror at Red Hook", presumably to try and give the film a Lovecraftian vibe. That whole "...Gorgo and Mormo of the thousand-faced moon." sort of thing. It doesn't really work, of course, but it's the kind of thing I keep running across in low budget horror movies from that time period.
That reminds me of something random. For years there's been this one epsiode of CBS Radio Mystery Theater circulating around the internet and p2p networks called The Horror Within and the file name claims it is by Lovecraft, but there's actually nothing Lovecraft in it. It's still being passed around that way. The main character is this little psycho Christian cum Satanist, there are a few strange and perhaps good lines in it, but the young man who plays the character did some other work for CBSRMT and there is this one episode (I've conveniently forgotten its name) where he sort of shacks up with this lady in California whose husband is this big-time occultist who's been away in India forever. It really carries the "porno-Derleth" feel I mentioned in connection with the Seal of R'lyeh story he wrote.
(I realize now why Derleth reminds me of porno: his stuff reminds me of the bits BETWEEN sex scenes, "the plot" which of course is either non-existent or better off not having existed in most porno films. Or perhaps it's more like the "plot" scenes of The Story of O (the book), which serve to interrupt the BDSM. But there is a sort of laid-back suave 70s feel to a lot of the Derleth I'm thinking of. Maybe his body of work remains an untapped resource for pornographers looking for a story to wrap around sex scenes, idk. Slow, meaningless, meandering, pointless... and those are the positive aspects. Not sure why I like him at all, but I do a little. Everyone should suffer through Lurker at the Threshold before completely dismissing him, imho.)