In regards to haunting illustrations, I think you can put me down for Charles Keeping's work for an odd little book called Weirdies, Weirdies, Weirdies: A Horrifying Concatenation of the Super-Sur-Real or Almost or Not-Quite Real
(try saying that thrice quickly), which I originally encountered in my middle school's library. The stories were odd enough, but I remember the illustrations being astoundingly unpleasant, yet fascinating, not unlike anyone who's ever gotten within thirty paces of a Scary Stories to Tell in the Dark
book. Things like a loving close-up of a carnivorous snail's mouth, a "photo" of a scowling woman with a piece of cursed hair pinned across her forehead, and so forth.
The book itself had that old-book smell that sometimes hinted that it had been forgotten for many years, and you were the first schmuck to disturb its rest in an epoch; that if there was something bad in the book, you'd be the only one to know. A lot of books printed in the late 1960s to mid 1970s do the same to me.
I found a gallery of Mr. Keeping's work here
, though the navigation is best described as excruciating. Thankfully, they bothered to put some of his black-and-white work in the "Gallery Tour" area, so if you can survive the dreadful Flash it's worth a look.