A new report claims to have found some more features in a leaked build of Windows 8.1, such as opening more than one Windows 8 app in a window and changes to how desktop apps look on the Start screen. From Neowin:

McAkins Online posts up word that, while examining the unnamed leaked build, they found a new option when right clicking on a Windows 8 app called “Open in a New Window”. It would appear that this will allow more than one Windows 8 apps to run in a window, something that has been requested by many current Windows 8 users.

Another small change that was spotted concerns how desktop apps are displayed on the Start screen. In Windows 8, the logo of a desktop app is shown on a background that has the current color of a user's Start screen. The leaked Windows 8.1 build shows that desktop app tiles now have the background color of the app logo itself.

 More new Windows 8.1 features spotted in leaked build