Can confirm on openSUSE 13.1 using 4.14.6-11.20-x86_64 from KDE:Current.

Observations:

1. RSS feed summaries do not display images;
2. RSS feeds set to display full article in preview pane display html/css, but no images/media or even empty placeholders thereof; and
3. Strangely, selecting Article>Open in Tab displays the page correctly, including images/media.

ATOM feeds do not work either. No images whatsoever in any feed, RSS/XML/ATOM.

This is a severely crippling bug for me.

Confirmed ATOM feeds don't work either. Some feeds do work though and I'm not sure why.

Never mind my previous comment. None of them are working; RSS or ATOM.

This is not a system-wide anomaly. A new user created on my system, all feeds display normally with images. There is apparently a per-user configuration/setting affecting the display of images in Akregator. Now, to find it... :/

Partially solved. Disabling AdBlock filters in Konqueror settings restores images to Akregator preview pane. It appears an Easylist filter is interfering.

However, I do not understand why only the preview pane was affected, not the in-app browser tabs. Does the preview pane renderer rewrite the media urls in such a manner that they get filtered out?

Yep. Disabled adblock in Konqueror. Must have enabled it at some point but I never use Konqueror so I wouldn't have guess that. I had to also remove any blocklists laying around in ~/.kde/share/apps/kmail2|kontact|khtml. But why are legitimate images getting blocked that are definitely not from any ad domains? Could it possibly be related to https://bugs.kde.org/show_bug.cgi?id=346338 ?

adblock implementation of konqueror/KDE doesn't fully support the syntax of the filters, so this will be a recurrent problem. Currently, the corset filter seams to break all images.

This bug has never been confirmed for a Kontact version that is based on KDE Frameworks, except possibly a Technology Preview version 5.0.x. Those versions differ significantly from the old 4.x series. Therefore, I plan to close it in around two or three months. In the meantime, it is set to WAITINGFORINFO to give reporters the opportunity to check if it is still valid. As soon as someone confirms it for a recent version (at least 5.1, ideally even more recent), I'll gladly reopen it.

Please understand that we lack the manpower to triage bugs reported for versions almost two years beyond their end of life.

Just as announced in my last comment, I close this bug. If you encounter it again in a recent version (at least 5.1 aka 15.12; preferably much more recent), please open a new one unless it already exists. Thank you for all your input.