Can't change piecemaker.png to anything else

I can't change the piecemaker images in the dropdown menus to anything other than 1 and 2. I have added a piecemaker3.png image to the directory where 1 and 2 are held but it doesn't appear to be picked up in the configuration drop down menus.

I have looked at the XML file that comes with the package but there's nothing obvious that points to a path.

The help document says to edit the 'xml construct' but doesn't specify what file to use/create or where it is/should be.

For clarity, I have got the application to load in the page and it runs two slides (which I can edit) but the blue and pink piecemaker images can't be changed in any obvious way.

Testing on a WAMP installation on a Win7 box - using both IE9 and Firefox4.

Edit: This is with a Joomla 1.5.22 installation.