rotate-wallpaper

#!/bin/bash
#=======================================================================================================================
# Description
#   Script to set a random wallpaper in Gnome 3/Unity. See
#   http://blog.yktoo.com/2011/10/gnome-3-ubuntu-1110-random-wallpaper.html for details.
# Synopsis
#   rotate-wallpaper
# Author
#   Dmitry Kann, http://yktoo.com/
# License
#   Public domain
#=======================================================================================================================

# Setup vars
dir_wallpapers="$HOME/Pictures/Wallpapers/iMac"  # Path to wallpaper directory

# Fill array with picture files (replace spaces with colons to fool the array)
files=( $(find "$dir_wallpapers" -type f \( -iname '*.jpeg' -o -iname '*.jpg' -o -iname '*.png' \) | sed s/' '/':'/g) )
# Get number of members in the array
N=${#files[@]}
# Randomize N
((N=RANDOM%N))
# Get the normal file name (change colons back to spaces)
file=${files[$N]//:/ }
# Change desktop wallpaper
gsettings set org.gnome.desktop.background picture-uri "file://$file"