It is possible to preview pictures and videos from some services directly within TweetDeck.

To enable this setting if it is not already set, go to Settings > Services and make sure Open photo links in web page is disabled. 

To preview pictures, click once to preview and then click on the image to go directly to the webpage.

To close the preview, click the X in the top-right corner or press Esc

The following image and video types are supported with this feature:

• TwitPic
• YFrog
• TweetPhoto
• Mobypicture
• 12Seconds
• Qik
• YouTube
• TwitVid
• Twitgoo
• Posterous
• Flickr