(EDIT: This fix I described was temporary. Hours later, the same messages fail to display images.)
I had this problem with images in iOS Mail, despite all privacy-protection options being off. Finally, after months and months of imageless messages in Mail on my iPhone, this fixed it for me:
*Reset Network Settings*
It's in Settings > General > Transfer or Reset iPhone > Reset > Reset Network Settings.
NOTE: This will flush your WiFi password (or possibly all of them). But it fixed the images issue in mail.
NOTE: After resetting network settings, messages you've already viewed in your inbox may not display their images, but newly received email messages will. (Or did for me.) I was, however, able to force an older message to display its images by archiving it, then undoing that action (returning it to the inbox), then marking it unread. After those steps, that message displayed its images.