So you use icewm and you do not want 1 wallpaper, but you want to have more? And you want them to auto switch after like, a hour, 2 hour or even a day?
Then use feh, and my script. Start with installing feh:

sudo apt-get install feh

NOTE: you need to have at least 3 wallpapers, and they need to be put in a folder, and should be named 1, 2, 3, ... 24, 25 etc. (extension is adaptable in the script).
Now, open gedit, nano, vim or whatever, and make a new file with a name you can remember. I will use .muur in this example. (Wallpaper literaly translated into dutch means muurpapier :P)

gedit ~/.muur

Then copy and paste the following in the file:

We need to edit a few variables, so do the following:

Change PAD to the folder where your wallpapers are. (In my home folder --> .muurpapier)
Change TIJD to the number of seconds between the wallpaper switch, 300 is 5 min, 600 is 10 min, 14400 is one day.
Change EXTENSIE to the extension of your wallpapers, like .jpeg, or .png.

Now save the file, and give it executable rights (chmod 755 .muur).
Then make sure it is started when icewm starts up (add ~/.muur& to ~/.icewm/startup, if you have named the file .muur and if it is in your home dir.)

Now logout and log back in, or press WIN+SPACE and type ~/.muur&, and you will have your changing wallpaper :D

Thats about it. Hope it is usable, and feel free to comment :)

(thanks to: http://tldp.org/HOWTO/Bash-Prompt-HOWTO/x700.html and http://islandlinux.org/howto/generate-random-numbers-bash-scripting for some bash info.)