How to change the icon in the application button

The documentation mentions that the application image can be changed,the one shown at the top-left in the shiny orb.How can one achive this.

 

Uses somethime like this in the constructor of your main RibbonWindow:

            Ribbon = new Ribbon();
            Stream stream = GetType().Module.Assembly.GetManifestResourceStream(GetType(), "Resources.mobiusStrip1BigShadow.png");
            BitmapImage bi = new BitmapImage();
            bi.BeginInit();
            bi.CacheOption = BitmapCacheOption.OnLoad;
            bi.StreamSource = stream;
            bi.EndInit();
            Ribbon.ApplicationButtonImage = bi;
            stream.Close();