• Your Windows build number: (Type ver at a Windows Command Prompt)
  Microsoft Windows [Version 10.0.17101.1000]

• What you're doing and what's happening: (Copy & paste specific commands and their output, or include screen shots)
  I run a file containing this (you could also just paste the three lines starting with printf):

#!/bin/bash
printf '\ePq#1NNNN#2NNNN#3NNNN$oooo'\
'#1oooo#2oooo-#3BBBB#1BBBB#2BBBB${{{{'\
'#3{{{{#1{{{{????\e\\'

The result is that it prints:
q#1NNNN#2NNNN#3NNNN$oooo#1oooo#2oooo-#3BBBB#1BBBB#2BBBB${{{{#3{{{{#1{{{{????

• What's wrong / what should be happening instead:
  Since ConHost doesn't support sixel graphics (at this time) it should be ignored and nothing should be printed. It should be as if the entire output of the program was sent to /dev/null.

"Non-graphics terminals generally silently ignore sixel escape sequences." -- https://en.wikipedia.org/wiki/Sixel

In WSLTTY (that supports sixel graphics) the program prints a 3x3 red, green and blue colored square:
brg
gbr
rgb

xterm in WSL Ubuntu with VcXsrv ignores sixel graphics unless started as a VT340 terminal: xterm -ti vt340, then it prints the colored square.