Twitter on Tuesday unveiled a series of design updates, a new app for the iPad and new versions of the application for other mobile devices.
"Starting today you can make your presence on Twitter more meaningful with new Twitter profiles," the company blog said. "Upload an all-new header photo on mobile apps for iPad, iPhone and Android or twitter.com, and the same image will appear whenever anyone views your profile on the web or these apps. You can upload your header photo, which appears above your Tweets, to express yourself instantly, anywhere."

Twitter's Jaikumar Ramanathan said one of the features is improved photo sharing.

"Photo streams for profiles display the images people have shared on Twitter," he wrote.

"Whenever you see a photo stream, swipe left or right through the thumbnails or tap to view photos in fullscreen mode. Android users can also get closer to photos with pinch-to-zoom."

Twitter, which allows its members to post brief comments, links or pictures, claims to have more than 140 million active users, with the largest number being in the United States.

A recent survey found one in seven Americans who go online use Twitter and eight% do so every day.