I was trying to configure my screensaver such, that it would display as only picture the desktop at the moment when the screensaver became active. In the KDE control center I chose the Slideshow screensaver (under Banners and Pictures) and in the setup I chose a specific directory as the media diretory (/home/your_user_name/Documents/images/desktop/). I also selected display one random image only. The media directory should be empty. Then I renamed /opt/kde3/bin/kslideshow.kss executable to kslideshow_ori.kss and created a shell script in the same directory that I named kslideshow.kss. The shell script looks like this:
!/bin/sh
import -window root /home/your_user_name/Documents/images/desktop/desktop.pcx
kslideshow_ori.kss
The import utility is from the ImageMagick package. Instead of the screensaver, the shell script gets activated when the time has come and a screenshot is saved in the /home/your_user_name/Documents/images/desktop directory. As this image is the only one it will be displayed by the subsequently called actual screensaver.