It would be a perfect distraction, pinning the blame on a group of parshmen. We go to war for years and years, never noticing the real villains, working quietly in my own camp. They watch me. Always. Waiting. I see their faces in mirrors. Symbols, twisted, inhuman…”
Dalinar glanced at Sadeas, and the two shared a disturbed look. Was Elhokar’s paranoia growing worse, or had it always been hidden? He saw phantom cabals in every shadow, and now—with the attempt on his life— he had proof to feed those worries.
-ch 58 pg 939
Shallan picked up the charcoal pencil and flipped through to a blank page in her sketchbook. She passed several pictures of the symbol-headed creatures, some set in this very room. They lurked around her, always. At some times, she thought she saw them in the corners of her eyes. At others, she could hear them whispering. She hadn’t dared speak back to them again.
-ch 70 pg 1097
“What of the creatures with the symbol heads?” Shallan asked. She flipped through her sketches, then held up an image of them. “Do you see them too? How are they related?”
Jasnah frowned, taking the image. “You see beings like this? In Shadesmar?”
“They appear in my drawings,” Shallan said. “They’re around me, Jasnah. You don’t see them? Am I—”
Jasnah held up a hand. “These are a type of spren, Shallan. They are related to what you do.” She tapped the desk softly. “Two orders of the Knights Radiant possessed inherent Soulcasting ability; it was based on their powers that the original fabrials were designed, I believe. I had assumed that you… But no, that obviously wouldn’t make sense. I see now.”
“What?”
“I will explain as I train you,” Jasnah said, handing back the sheet. “You will need a greater foundation before you can grasp it. Suffice it to say that each Radiant’s abilities were tied to the spren.”
-ch 72 pg 1112
It's odd, judging by Jasnah's reaction, she knows of them, but doesn't deal with them herself. It might mean Elhokar would be of the same Order as Shallan (6, Shash, was the guess someone put forth earlier, which sounded good to me and another as well) or simply that they only appear to some Orders and not others. But yeah, I'm definitely counting him as a Knight Radiant candidate as well. Anyone else notice that Dalinar got his plate to glow a bit early in the book?
Dalinar held back the claw and matched its strength, a figure in dark, silvery metal that almost seemed to glow. The beast trumpeted above, and Dalinar bellowed back a powerful, defiant yell.
-ch13 pg 230
Standing beneath the massive chasmfiend, holding it back from killing his nephew, Plate glowing. That image was fixed in Adolin’s memory.
-Adolin thinking back on it in ch15 pg252
Of course, that might just have been leaking Stormlight, or the sunlight reflected off of it , but they usually say that specifically.
What I just found quite interesting by re-reading something Jasnah says is:
Jasnah frowned, taking the image. “You see beings like this? In Shadesmar?”
She either finds it very odd to find those spren in Shadesmar, or knows they exist there and for Shallan to have seen them is weird. (But the spren weren't seen in Shadesmar, so it could have just been Jasnah being confused at them being there. Maybe I'm reading too much into that line).
As far as the quote about Dalinar's armor, I don't think it was Stormlight leaking, like you said, the characters always talk about the Stormlight leaking (and they know what it looks like, this, I think, was something different). For it to imprint a mental image to Adolin's memory, it must have been very out of the ordinary.