First appeared in Asimov's. Reprinted (perhaps the most frequent) by Gardner Dozois, Jim Turner, Sheila Williams, John Gregory Betancourt, and Colin Azariah-Kribbs.
The title indicates it is a play off of H.P. Lovecraft's "Pickman's Model" where the narrator learns that a talented artist on the outs with his artist community because of his grotesque drawing has truly been seeing such visions.
Although the story states it explicitly, Watt-Evans' Pickman is anything but talented. He'd bought a second-hand Miskatonic Data System modem and it changed his poor grammar/spelling into something more elegant if archaic. Whereas Pickman tells a person to do something crude, the modem phrases it in a less direct manner. Pickman is disturbed but not enough to get a new modem....
Maybe you can guess what happens next. How else can a Cthulhu story end? This tale gains humor/power when compared to its original.