It's interesting, being a fan of H. P. Lovecraft, to look at early 20th century expressionist art and realize that's what he was talking about.
Egon Schiele, for example; that's a dude who's looked into the face of Hastur and lost a few sanity points. And if James Ensor never took a dream-journey to the shifting streets of Carcosa, there is no reason in the world. Franz Marc clearly spend more time in the Dreamlands than among us.
HPLovecraft.com has a page up now of Lovecraft's comments on specific artists that inspired him, and Tor has its own synopsis of those artists. Interesting, if very brief, reading.
And though it's no longer emblematic of the times, it isn't as if the Old Ones stopped fucking with humanity after the rough beast stopped slouching toward Bethlehem. I dunno what Francis Bacon saw when he closed his eyes, but what he let out scares the crap out of me.