怎么给窗口增加背景图片？

我的Ext.Window要怎么才可以给他增加一个背景图片

bodyStyle : 'padding:25px;background-image:url(../images/bg.jpg);background-position:right bottom;background-repeat:no-repeat;'

加个bodyStyle:'cssName'//
[code="java"]
.cssNmae{
....
background-image:url(xxx.jpg);//定义背景图片
....
}

[/code]

[code="java"]
bodyStyle : String/Object/Function
Custom CSS styles to be applied to the body element in the format expected by Ext.Element.applyStyles (defaults to nu...
Custom CSS styles to be applied to the body element in the format expected by Ext.Element.applyStyles (defaults to null).
[/code]