I agree that there has to be something visual to find. Reflecting on the old MAD Magazine folding images and the many references to mirrors and perspective I have read by people who may or may not be privy to the true solution, I made a few attempts at manipulating the image to see if anything popped out.
I put together an album. I included some descriptions in the captions. Please take a look and see if anything jumps out at you.
https://imgur.com/a/aJgyj
regarding the infrared effect (Night vision) the rabbit mentioned that idea just to group the flames which may imply that evey flame you can see with infrared is a real flame (1) the others (0)
when you apply the infrared effect (which means you can see at night without any light) then the image looks like this: (Green colour is dominant)
https://imgur.com/a/tQC0W
it's the same technique used in military binoculars in order to see the enemy at night.
the idea that you mention to mirror and blend images trying to get something out is more suitable and possible if it was a digital art, but in case of painting it would be so difficult for the creators to hide something using that technique.
But i am still skeptical because there is the word Fold (Fo on the dove and Ld on the phoenix)
it may imply that we have to fold the image or blend a part of it, or it could refer to that 3-D Fold in the middle (blue and red tiles)
it's important too to answer these two questions:
1) who is inside the key hole mirror, the face inside that keyhole is either a reflection of the Top part of the Queen piece or a reflection of the Knight.
The white rabbit posted a hint "Who are you in these puzzles? Sometimes something is small and sometimes something is big"
https://imgur.com/3URkIsv
for me i see the white piece represents Queen Alice and the face in the mirror its reflection (maybe that key hole is the rabbit hole and represents the first chapter of the story)
2) if we can see an image in second mirror (that with blue pyramid), Then, where is the real object of that reflection? and those letters in the image how we can read it?
BTW: in your first image there is (Af) in the bottom right corner (inside the flame), i've seen it before but i don't know what does it mean.