Dropbox today announced Carousel, a product to store and manage your photos and videos. It incorporates features from Snapjoy, a photo startup that Dropbox acquired in December 2012. The launch of Carousel represents a bid for Dropbox to diversify its lineup of products — and potential revenue streams — as it prepares for an expected initial public offering of its stock. At an event in San Francisco, Mailbox founder Gentry Underwood showed off the service, which organizes your photos and videos into an app for Android and iOS.