An observation:
If you number the flames starting at 1, then every even numbered flame's length produces this consistent pattern all around the image:
0 1 1 0 1 1 0 1 1 0 1 1 .... (short = 0, tall = 1)
The 011 pattern repeats 25 times but only for the lengths.
The odd lengths (the bits between the 011 pattern) seem random and all color bits seem random too.
So the information encoded in the lengths cannot possibly be part of a private key (at least not the even numbered ones).
Here is what I got for the odd flame heights in the same order as the pattern.
0101010100110000111100001101101010111111111100010000111101111110101100001101
I have run it through a few scripts and cannot get anything useful out of it. If you break it up into groups of 4 and assign letters to them, I still don't see anything useful.
0101 0101 0011 0000 1111 0000 1101 1010 1011 1111 1111 0001 0000 1111 0111 1110 1011 0000 1101
I I N E F E V V T F F S E F A R T E D <--- This is the best one I got.
There has got to be something hidden in the odd flame heights. It wouldn't make sense to use the colors because you need those for the private key.
I converted the 0's and 1's to morse code and tried that as well.
.-.-.-.-..--....----....--.--.-.-.----------...-....----.------.-.--....--.-
ARCANE IONS MAKE TWO MOVES ONTO MAP I WET.