KDE 4: How to remove the wallpaper.

[Andrea]

I have a very basic question:

I cannot find where to remove the background image in KDE 4.

If I do right click on the desktop and the select "configure desktop",

I have:

wallpaper image, (no image/file selected), the preview is gray but still on the desktop I have a 
sort of blue see/sky with a lot of circles and stars/rays.

where can I remove it?

I must be blind but I have not found anything..... please.

Andrea