#!/bin/bash
#
# Write by Karfield
#
# Free to use it!)
#
BING=http://www.bing.com
TMPFILE=/tmp/bing.html
WALLPAPER=/home/$USER/Downloads/bing.jpg
echo “Try to get the BING page…”
wget -q $BING -O $TMPFILE
! [ -e $TMPFILE ] && exit;
URL=$BING$(sed -n “s/\(.*\)g_img={url\:’\([0-9a-Z?=%_-\\/\\.]*\)’\,id\(.*\)/\2/p” < $TMPFILE)
echo "Get the picture's URL = "$URL
rm $TMPFILE
mv $WALLPAPER{,-old}
echo "Download the wallpaper… "
wget -q $URL -O $WALLPAPER
if [ -e $WALLPAPER ]; then
echo "We got it, set the background…"
gconftool-2 –type string –set /desktop/gnome/background/picture_filename $WALLPAPER
gconftool-2 –type string –set /desktop/gnome/background/picture_options zoom
gconftool-2 –type string –set /desktop/gnome/background/primary_color black
fi

You can save the code as update_bing_wallpaper.sh, don't forget to change the file mode as "u+x". And run it to change your background.

sed ‘s/centered/zoom/g’ -i bing_wallpaper.php

in order to set the wallpaper fullscreen, since the images from bing.com is pretty small compared to the monitors used today. Even on netbooks.