This is an easy one. Although you can perform background auto change from KDE control center, it may be usefull to have a script to do the task. You can use this script to create a link in your desktop to change the background image when you want.

The KDE applications can be controlled by scripts via the DCOP mechanism. From the Wikipedia:

DCOP, which stands for Desktop COmmunication Protocol, is a light-weight interprocess and software componentry communication system. The main point of this system is to allow applications to interoperate, and to share complex tasks. Essentially, DCOP is a ‘remote control’ system, which allows an application or a script to enlist the help of other applications. It is built on top of the X Window System’s Inter-Client Exchange protocol.

Let’s begin with the script, here is the code:

#!/bin/bash
dcop kdesktop KBackgroundIface changeWallpaper

Now, you have to create a list of backgrounds using KDE’s control center. First open kcontrol, browse to Appearance & Themes > Background and select Slide Show. Click on Settings

Just create the list, and the script is ready to go.

• signature.txt: you should point your mail client to this one
• signature.tpl: here is the common text to display, something like “xmms is now playing:“
• signature.sh: the script first copies the contents of the template file to the final signature file, and then adds the current song as a new line.

Download signature.sh:

#!/bin/sh
cat /home/etd/scripts/signature.tpl > /home/etd/scripts/signature.txt
echo $1 >> /home/etd/scripts/signature.txt

you only need to call the script using the change song xmms builtin plugin.

From this page:

To refresh the backdrop with a new random image from the list just run the xfdesktop command again, e.g. from a terminal or the run dialog, or xfdesktop [-reload].

What we have to do now is to create a shell script that runs xfdesktop -reload and to add a cron job to run it.

Let’s begin with the script, here is the code:

#!/bin/bash

#check if we are under xfce
for foo in  `ps aux | grep xfdesktop | grep -v grep | awk '{print $11}'`;
do
  if [ $foo == "xfdesktop" ];
  then
    #reload xfdesktop
    export DISPLAY=:0
    xfdesktop -reload
  fi;
done;

Now we need to add a line in the crontab, run the script every 25 minutes:
*/25 * * * * /home/etd/scripts/xfdesktop-reload.sh

NOTE: If someone finds an easier way to check whether the user is running Xfce or not, please let me know.