Twitter has redesigned its interface to automatically display photos from promoted tweets and the first frame of videos in the news feed. Previously, users had to click the link. 
This adopts a format similar to Facebook's news feed, allowing advertisers to place large display ads directly within users' news feeds. (Photo shows an example of a Samsung promoted tweet)
Details at AdAge→http://bit.ly/1aFgzVC
Promoted Tweets Get Big Boost In Twitter Redesign
From Text-Only to Big, Facebook-Like Display Ads In the Timeline
Published: October 30, 2013