Hello Susanne,
I'm not sure if this will help or not, but to display a PNG, this is what I
use:
<div id="imgDAoCLogo"
style="height:98px;width:174px;position:static;fil ter

rogid

XImageTransform.Microsoft.AlphaImageLo ader(src='images/DAoC_Logo.png',
sizingMethod='scale');"></div>
The PNG height and width is entered in the style information. I have
different images being displayed in a table and I just use the div's as
containers. Not sure how that's going to work since you're using a PNG as a
table background image.
--Tim