The announcement was made by Twitter CEO Dick Costolo who is set to speak at D9 on Wednesday. After the launch of their own photo sharing service they will be in direct competition with current photo sharing services like TwitPic and Yfrog.
The process wasn’t smooth for adding a picture to your tweet, users first had to upload picture at any of the photo sharing service and then paste the link in their tweet. It’s a lengthy process, some desktop clients offer built-in media attachment functionality and TweetDeck was on top of list. If your remember Twitter stopped developers from making third-party Twitter clients anymore. And they also acquired TweetDeck, which they probably will launch as an official Twitter client soon.