Source: http://www.labnol.org/internet/email/google-news-email-alerts-get-images/4560/
Google has slightly enhanced their email alerts system and the messages now include images next to stories that are either sourced from Google News or YouTube Videos (see screenshots).
To see these image thumbnails, make sure you are subscribed to HTML format email instead of plain text. Also read this Google Alerts tutorial to get more out of the service.
Google News Alerts inside Gmail
Google News Alerts email in Microsoft Outlook
Google Email Alerts Now Include Images - Digital Inspiration