Another unreliable illstration in D&D 3.0 monster manual was the Allip. This undead is described as “looking just like when it was alive, but with an insane grimace on its face, eyes burning with fear and the lower part of the body blurring into nothingness.” The illustration, however, depicts something that look like a vagualy humanoid tattered in black rag, without eyes or a face. (you can find the trope here)
Unsatisfied by the picture to show in my RPG campaign, I had a selfportrait and maked up with Photoshop, very quickly, to show some new good idea. I still really like this, even through years.