Here is an example of the background image html needed to put a background image in your infoboxes.
[xcode] <table background="http://www.clantoolz.com/images/force_bkgrd.gif"> <tr> <td> <font size="+1" color="White"> This text is over the background image.<br> This text is over the background image.<br> This text is over the background image.<br> This text is over the background image. </font> </td> </tr> </table> [/xcode]