This image issue may be more of a quirk when using phpBB as a forum hosting program, which is what Eric (Mudbug) uses. Most notably when embedding an image link inside a quote box. Not my area of expertise, just anecdotal observation.
We have many browsers here at work and the images are not visible in Windows 7 or 10 running:
Firefox
Chrome
IE11
Edge
and on the Iphone 8 running:
Safari
Puffin
Hoot