*Update on 9/4/2013 11.40pm: Google has confirmed in an official blog post that the new card-based user interface of Play Store will start rolling out today and over the next few weeks. The update will be available for smartphones and tablets running on Android 2.2 (Froyo) and above.
Google has apparently been working on a redesign to Android's Google Play store that will include brighter colors and bigger images, not to mention a clean new interface.
The leak comes courtesy of Droid Life via YouTube employee, Eileen Rivera, who leaked the screenshot on her Google+ profile last weekend in a post titled, "oh hello, new Google Play store redesign" (the post has since been taken down). The image shows a cleaner looking menu screen on Google Play. The dog bowl and bone icon seen in the image is Google's internal symbol for when it is working on a product redesign (a reference to dogfooding)
Google is likely to unveil the revamped design at its I/O Developers Conference in May.