[SOLVED]Can't change login background

[SenorSalad]

I recently installed Debian 8 with the Xfce Desktop Environment. I don't like the background in the login screen and want to change it. After some Googling I discovered that the path to the background is stored in the file /etc/lightdm/lightdm-gtk-greeter.conf. Unfortunately, whenever I change the background field I'm left with a black background during login. (Yes, I triple checked that I spelt the path correctly). Does the login background have to meet some criteria I don't know about, like being a certain resolution?

EDIT: Here's the content of /etc/lightdm/lightdm-gtk-greeter.conf:

Code: Select all

#
# background = Background file to use, either an image path or a color (e.g. #772953)
# theme-name = GTK+ theme to use
# icon-theme-name = Icon theme to use
# font-name = Font to use
# xft-antialias = Whether to antialias Xft fonts (true or false)
# xft-dpi = Resolution for Xft in dots per inch (e.g. 96)
# xft-hintstyle = What degree of hinting to use (none, slight, medium, or hintfull)
# xft-rgba = Type of subpixel antialiasing (none, rgb, bgr, vrgb or vbgr)
# show-indicators = semi-colon ";" separated list of allowed indicator modules. Built-in indicators include "~a11y", "~language", "~session", "~power". Unity indicators can be represented by short name (e.g. "sound", "power"), service file name, or absolute path
# show-clock (true or false)
# clock-format = strftime-format string, e.g. %H:%M
# keyboard = command to launch on-screen keyboard
# position = main window position: x y
# default-user-image = Image used as default user icon, path or #icon-name
# screensaver-timeout = Timeout (in seconds) until the screen blanks when the greeter is called as lockscreen
# 
[greeter]
background=/usr/share/images/custom/forest.jpg
theme-name=Adwaita
#icon-theme-name=
#font-name=
xft-antialias=true
#xft-dpi=
xft-hintstyle=hintfull
xft-rgba=rgb
show-indicators=~language;~session;~power
show-clock=true
#clock-format=
#keyboard=
#position=
#screensaver-timeout=

EDIT2: I solved this issue by making the desired background world readable.