Also, that image did not post in Q 1543, it was posted in the Neon Revolt thread with text coming from Q 1543.
There's probably not much to be profited from further analysis of the obvious color banding within it, then...
BTW, unlike the simply darkened and contrast-reduced "hidden" image in #499, this one was "inverted" (IOW, a "negative") -- easily recovered thru hexidecimal calcuation -- and, even more simply recoverable by using the "Invert" function of an open-source IPP program like "NIH Image"...
TXnMA