background image for AIR application

<?xml version="1.0" encoding="utf-8"?>
<mx:WindowedApplication name="WindowedApplication_backgroundImage_test"
        xmlns:mx="http://www.adobe.com/2006/mxml" layout="vertical" verticalAlign="middle">

    <mx:Style>
        WindowedApplication {
            backgroundColor: white;
            backgroundImage: ClassReference("mx.skins.halo.ApplicationBackground");
        }
    </mx:Style>

</mx:WindowedApplication>