[funkydunk]

This is possible.

There are a few things to change though:

Firstly:
Set the image as a background in the ski1.css syle sheet for background.

.background {
background-image: url(images/background.gif)
}

Then you need to change the part in dialog.tpl that contains:

<TR><TD class=DialogBorder><TABLE border=0 cellPadding=10 cellSpacing=0 width="100%">
<TR><TD bgColor=#FFFFFF>{$content}

</TD></TR>

to:

<TR><TD class=DialogBorder><TABLE border=0 cellPadding=10 cellSpacing=0 width="100%">
<TR><TD class="background">{$content}

</TD></TR>

Then you will need to take out the background colour settings in the skin1.css file until you get to the right effect. The bits to concern about are:

WhiteLine - this is the background to the search box
Table Top - This is the area above the dialog box