Nifty Buttons with icons

I am trying to implement a button with icon on it. Currently my button control is something like this



[java]

<control name="button" label="CLICK ME" id="click01" paddingTop="4px" align="center" valign="bottom">

<interact onClick="click()"/>

</control>

[/java]



how can I replace the button text CLICK ME with an image?