Let's start with this totally surreal, pseudo-photograph by CthulhuCthulhu, a store dedicated to cthulhian creepiness. Have you ever wondered why there was nothing in the family album about the obscure Innsmouth branch? This unique postcard gives you the answer! This amphibian-looking fellow may well be Captain Obed Marsh himself -and slightly reminiscent of Captain Beefheart's Trout mask replica album cover.
Scythemantis is quite different. His work is cartoonish and playful, paying an imaginative homage to the Great Race of Yith. Do these yithian tentacles hold the Pnakotic Manuscripts? Scythemantis's work is well-versed and rich in details so I guess the answer is yes.
Finally, I should remind you to check this older post about Bradley W.Schenck's magnificent work at Ars Celtica. Some of the best Mythos-inspired artwork lurks there, sleeping but not dead!