Oh holy hell, I can't believe I found this! I have this Dragon Magazine (back when, you know, it still existed) and let me tell you, this cover definitely made me stop and stare for a good five minutes. This REALLY nails the horrors of the illithiad race, how downright scary and cruel mindflayers are by their very nature and it still gives me creepy-crawlies to see it. It was pretty much this image that made me sympathize for all the classes/races out there bent on destroying mindflayers. You sir, are a master.
The illithid looks so evil, and I love the way its claws are grasping the shoulders of his victim.
I don't think I've seen anyone else showing mind flayer tentacles going into a mouth before, but I think it makes it look more like the illithid has grabbed any part of the head it can get to to suck the victim up into its maw.