Need help with weather monitor background

Hi,

I managed to start up weather monitor, it shows correct icon and temerature. However the background is weird in all of the default skins, also in the one I'm working on. The preview in the properties dialog box looks fine:


What you see in the picture is that I tried to create a real background in png format instead of the transparent png, the preview renders it well, while on the taskbar it shows the wallpaper below the taskbar, in the size of the background.png as if a window was cut into the taskbar.

What do I do wrong?