Yesterday, Google sent out their first Google News Publisher newsletter and it has some nice information, but one big tidbit on the algorithm side that is very important for Google News publishers.
Google News previously only would crawl, index and display images from a news publisher when the image was hosted on the publisher's domain name. Now that has changed and even if you host the images on a separate domain, like we started doing here when I migrated to HTTPS.
Google said in the newsletter:
An update on image crawlIn the past, if your images were hosted off your website's domain, it was very unlikely we'd crawl them for Google News.
We recently implemented an update to our image crawl algorithm, and are now able to crawl off-domain images. If it works better for your team to host your images on a different domain than your news website, you can now feel free to make that change!
So maybe you'll start seeing these article images in the news search results again.
Forum discussion at Google+ & Google News Help.