Broken Icons in Settings Manager
I noticed that if the Icon parameter on desktop file is set to specific path or just icon filename like this
Icon=Picture.png
or
Icon=/usr/share/pixmaps/Picture.png
The icon on xfce settings manager was broken. However if the Icon parameter is set to just filename without file extension like this
Icon=Picture
The icon was shown on xfce settings manager. Please allow specific path or icon filename on "Icon=" of desktop file to show icons to xfce settings manager