如何修改panel的背景

我想换成我自己的图片，要怎么设计呀？
[b]问题补充：[/b]
修改css那不是所有的都变了。我只想修改当前panel的

设置 baseCls属性
[code="js"]items: [
{title:"panel内容", baseCls:"mybase"}
][/code]
CSS:
.mybase
{
background-image: url('图片路径');
}

找到修饰panel的CSS文件，然后修改这个CSS样式文件啊

设置panel配置属性如下之一
baseCls:"classname"
cls:"classname"
ctCls:"classname"

baseCls : String
The base CSS class to apply to this panel's element (defaults to 'x-panel').

cls : String
An optional extra CSS class that will be added to this component's Element (defaults to ''). This can be useful for adding customized styles to the component or any of its children using standard CSS rules.

ctCls : String
An optional extra CSS class that will be added to this component's container (defaults to ''). This can be useful for adding customized styles to the container or any of its children using standard CSS rules.