If you're willing to mess with the core code, here's one solution:
In the file program/js/app.js change lines 1168 & 1169 (in case your version is different, this is in the function show_message) from this:
if (safe)
add_url = '&_safe=1';
to this:
add_url += '&_safe=1';
Removing the condition 'if (safe)' and changing '=' to '+=' causes it to pass the 'safe' url every time so all images are displayed as if the 'display images' link was clicked. Of course you'll have to keep track of this as future versions come out and re-fix it if necessary. Hopefully it'll get developed in and be switchable in the config or user prefs. What would be even better would be if it could be per sender:)