I think it is simply because of their alt tags. For example:
South Korea’s Deputy Foreign Minister Soon Min-Soon arrives in Beijing. US and South Korean envoys held talks with China aimed at coaxing North Korea back into six-party nuclear talks as the CIA said the Stalinist regime could re-start long-range missile testing.
The algorithm google uses to decide on the pictures obviously considers the alt text superior to the page text in determing the subject matter of an image. Long alt tags lead to more appearances in Google News. I wonder if they did it on purpose?