I don't know if you've heard but the crew of the Sci-Fi Channel's show Hollywood Treasure (a reality show about a movie memorabilia consignment house) visited a gentleman who inherited much of the science fiction and fantasy collection of Forrest J Ackerman.
While going through the items he was willing to sell, he offered what he claimed was the original poster-sized cover art for The King in Yellow, supposedly painted by Chambers himself. The appraiser was unimpressed, because he mostly moves items from mainstream properties and didn't think there would be much interest. He reluctantly took the art, and estimated it would bring $400-600. At the auction that ends the show, phone bidding finished at $7000.
The episode seems to either be called "Joe's Judgement Day" or "Spidey Cents" (the latter only on the SF Channel's website). It doesn't look like video is available legally yet.
The auction listing for the piece is still available at the Profiles in History website. Here's a look at the actual art:
It's a beautiful piece that draws on the traditional iconography of the greek god Thanatos as a cloaked, winged figure carrying an inverted torch. What it doesn't have is the inverted torch with swirling flames, a reversed interpretation of the Rod of Asclepius, that I used as the inspiration for my alternative interpretation of the Yellow Sign . Sadly, it appears that I, like so many before me, didn't appreciate the true nature of the King.