Well, at least in the ARC, the "Head on a pole" scene is nestled nicely between the following lines:
Kellhus: "What was my revelation? What secret could It whisper into an ear so small as mine?"
Scene.
Proyas: "What was your revelation?"
Seemingly, this is explaining the revelation. Of course, this could be misdirection, but I think it's likely not. It's a cryptic, but later, Kellhus' own POV states "He hand learned of the head on the pole." (Page 120 of the ARC.) He says it in a way that I doubt this is common knowledge, put after a list of arcana such as Diamos, Metagnosis and the Thousand-fold Thought. After speaking of grasping the metaphysics of Creations and returning from Hell with trophies. They would seem to be ciphrang in the vision though, or at least, so it seems to me from the description.