Twitter users will soon be able to post, search for and view photos directly on the social network, company CEO Dick Costolo said this week at the D9 conference. To date, San Francisco-based Twitter has been focused on allowing consumers to post short text messages. To share pictures on Twitter, users typically upload them to another site, such as Yfrog, and post a short link to those photos on Twitter. But in the next several weeks, Twitter will roll out a new feature that allows users to upload photos directly through its website, Costolo said. Soon afterward, the company plans to add the feature to the applications it makes for smartphones such as Apple's ( AAPL ) iPhone.