Blend for Visual Studio 2013 understands only two languages

Blend udnerstands HTML and XAML only.
You can use C#, Visual Basic or C++ for most XAML Store apps and Javascript for HTML Store Apps. XAML is of course more versatile but requires a steeper learning curve.

• HTML Store Apps

1. Universal Apps

          Blank App
          Hub/Pivot
          Navigation App

    2.  Windows Apps

          Blank App
          Grid App
          Split App
          Hub App
          Navigation App
 
   3. Windows Phone Apps
    
        Blank App
        Pivot App
        Navigation App

• XAML Store Apps

1.  Universal Apps

        Blank APP
        Hub App
        Class Library (Portable for Universal App)
        Windows Runtime Component (Portable for Universal App)
        Windows Runtime Component(Universal App)
  
    2.   Windows Apps
    

         Blank App

         Hub App

         Grid App

         Split App

         Class Library

         Windows Runtime Component

   

   3  Windows Phone Apps
    
        Blank App
        Hub App
        Pivot App
        WebView App
        Class Library
        Windows Runtime Component
        Blank App (Windows Phone Silverlight)
        Databound App (Windows Phone Silverlight)
        Control Library (Windows Phone Silverlight)
        Panorama App (Windows Phone Silverlight)
        Pivot app(Windows Phone Silverlight)