I once participated in adding Arabic to wallch and I just love this program.
What is Wallch?
Wallch is a wallpaper changer. It doesn’t simply change your desktop background with the wallpapers that you have in your hard disk, though. While it does that well by monitoring the folder that you have selected for new or deleted pictures, it has lots of features, like Picture of the day, Live Earth, Wallpaper Clocks and Live Website!
Wallch is Open Source, which means that anyone can download and inspect the code. It currently works on Gnome (with or without Unity integration), LXDE, XFCE and Mate. Wallch version 4.0 is now available for download.
http://melloristudio.com/wallch/
you can do it manually by downloading quick icon i did from here and replacing it in “/usr/share/wallch/files/” or simply download and run the script or just copying it
#!/bin/bash
echo “Changing Wallch indicator icon to mono”
wget https://www.dropbox.com/s/vi7emuehp7krayj/indicator_ambiance_normal.png
sudo cp /usr/share/wallch/files/indicator_ambiance_normal.png /usr/share/wallch/files/indicator_ambiance_normal_original.png
sudo cp indicator_ambiance_normal.png /usr/share/wallch/files/
rm indicator_ambiance_normal.png
echo “Done”
have fun.