Playing with newsboat and W3M as pager, I've been checking Terminals that support W3M images without flickering when scrolling, or other display artifacts. Unfortunately I've only found one, Xterm.
There are a lot of publications on the web proposing arcane hacks, might not work for you's, unmaintained stuff, etc. but in reality there's no cut and dried solution for W3M's own image rendering that works on all terminal emulators.
The working solution I found was sixel support, see arewesixelyet.com
Today the winner is: Alacritty with W3M's img2sixel option