A WebmasterWorld thread reports one member noticing receiving images in his Google Alerts from Google Blog search. It seems to be an extension of how Google News shows images near some articles. But in this case, this searcher is saying the images are near blog post results from Google Blog search.
I am not too sure if the user is confused in how he or she is using Google Alerts. I think that this person subscribed to Google Alerts and signed up for both News alerts and blog alerts. Google News often shows images near articles, but Blog Search does not - as far as I know.
Is it possible that Google Blog search is now showing images near the blog results? Yes, why not? But is it happening?
Forum discussion at WebmasterWorld.