I just flipped through an art book again which my father bought long ago, it's about the mainly Sci-Fi paintings of artist Tim White. There is some cover art in there that Tim created for a series of Lovecraft paperbacks, some are pretty nice so maybe you can find some inspiration for your own creations, games, or whatever.
Now that I'm writing this, I also remember a series of cool Lovecraft cover art by Michael Whelan, might as well post it here as well
Tim White:
Mountains of Madness:
I don't know what kind of creature this is supposed to be, in MoM there were only Elder Things and the Shoggoth IIRC.
The Lurking Fear:
Dagon: (it looks more like Tsathoggua doesn' it?)
I like the composition of this painting, the light shinging through the cave openeing in the background makes you feel that the cave is massive.
Devil's Dream: (Found no better scan)
I have no idea why there's a bunch of small green reptilian monsters fondling a naked woman in front of a red moon
Tales of Cthulhu:
I think this is supposed to be Tsathoggua.
Mask of Cthulhu:
A Shoggoth or Formless Spawn maybe? Edit: Probably a Shoggoth, the human leftovers in front are mentioned in several CoC adventure moduls as a sure sign that a Shoggoth is around, leaving bits of bone, jewelry etc. in slimy lumps behind after a meal.
Trail of Cthulhu: (My favourite)
Looks like Shoggoth pit to me, very scary, imagine being a prisoner of some nameless cult, standing at the edge of a large hole in the ground that leads into darkess, at the bottom of which you can see a mass of wirngling tentacles, eyes and fanged mouths
New Tales of Cthulhu Mythos:
Erm.. yeah, I don't wanna know what the backstory here is...
Michael Whelan: (This is one wide painting, with several novels taking a part of it as their covers.
I don't think there's any connection to any actual Lovecraft stories, maybe the painting elements correspond to stories from other authors, all I know is that one of the books is "The Lurking Fear", it has the Mr.-Hyde-like guy behind the window as a cover. Still, I like that demonic caterpillar, the Mr. Hyde-like figure, and the foreboding cloaked figure standing in the background gesturing, maybe part of some dark ritual
BTW, I just called that window-figure Mr. Hyde because when I first saw these painting as a kid or teenager, I somehow imagined that he had a top hat on
Also, that wooden crate with the arms sticking out from it reminds me of some Scene of Horror for Strange Aeons which some user has crafted here, actually I don't think that can be a coincidence
The trees with the red eyes, the finger/claw/bone-like stone structures sticking out from the grey slime, and the skulls on sticks with red marking to the right would all make great scenery items for horror games.
The caterpillar reminds me of the water dragon in "Spacehunter: Adventures in the Forbidden Zone", in the scenes where the Amazons attack Wolff and Niki (kinda obscure reference!)
Where do these tentacle-barb things behind the bricks come from? Are they part of some unseen creature?
Michael Whelan also made a series of covers for John Carter novels, as well as the famous cover art for Sepultura's "Chaos A.D." record. Worth a look if you can find a book with his paintings.