A quick post to talk about François Launet, aka Goomi. His particular field of expertise is Cthulhu and friends, but I wouldn’t bet too much on his material for direct inspiration for your unspeakable campaigns, as he managed to make the Old Ones funny and likeable!
Have a look at The Unspeakable Vault (of Doom), his web site, where over 500 comics have been published, his two books compiling this material or the extension to Munchkin Cthulhu he made the art for!
I just discovered the website of Olivier Sanfilippo, an amazingly gifted artist. His work primarily deals with characters and landscapes and convey a subtle mix of mysticism and lurking danger, which makes them very inspiring to me. He’s also done some of the most beautiful maps I’ve ever seen. He’s done plenty of work with RPG companies (illustrating for Shadows of Esteren and other french RPGs). It’s the kind of work so inspiring you can start imagining a whole world just by looking at a single picture.