Switching backgrounds in gnome

Surprisingly, gnome doesn't have a built in background switcher to change the background every N minutes. I found some on the 'net but didn't like any i found, so wrote my own as i'm want to do.

I have it start every time i log in by going to System -> Preferences -> Personal -> Sessions (Add):

#! /bin/bash

# System -> Preferences -> Personal -> Sessions

function dohelp() {
 echo "$0 has three optional arguments."
 echo "'-d dirname' to specify the directory to examine (~/Backgrounds"
 echo "    by default)."
 echo "'-s sleep' to specify the number of seconds to sleep between"
 echo "    changing backgrounds (1800 (half an hour) by default)."
 echo "'-m method' to specify the method of displaying the images."
 echo "    Values are:"
 echo "    'zoom' to fill the screen and chop off any extra from the two"
 echo "        edges that overflow.  Aspect ratio is maintained.  This is"
 echo "        the default."
 echo "    'scaled' to fit the image to two edges and fill with the"
 echo "        background color on the two edges that don't reach."
 echo "        Aspect ratio is maintained."
 echo "    'streched' to fit the image to all four edges while not"
 echo "         maintaining the aspect ratio."
 echo "    'centered' to place on the screen with no scaling at all"
 echo "    'wallpaper' to repeat the image as many times as it will fit"
 echo "        with no scaling."
 echo "    One can also have picture-specific methods by creating a file"
 echo "    prefixed by a dot ".DSC0001.jpg for example" that has one word"
 echo "    in it, either zoom, scaled, streched, centered, or wallpaper."
 echo "    If none is specified, the default is used."
 exit
}

DIRNAME=~/Backgrounds
SLEEP=1800
METHOD=zoom

while getopts 'd:s:m:h' OPTION
do
 case $OPTION in
 d) DIRNAME="$OPTARG" ;;
 s) SLEEP="$OPTARG" ;;
 s) METHOD="$OPTARG" ;;
 h) dohelp ;;
 ?) echo "Usage: [-d directory] [-s sleep] [-m method]" >&2
     exit 2
     ;;
 esac
done

FILENAME=/desktop/gnome/background/picture_filename
OPTIONS=/desktop/gnome/background/picture_options

method=$METHOD
gconftool-2 --type string --set $OPTIONS $method

while true
do
 # (re)read directory to pick up any new files
 for i in $DIRNAME/*
 do
 filename=${i#$DIRNAME/}
 # echo $filename

 methodfile=$DIRNAME/.$filename
 if [[ -e $methodfile ]]
 then
     # echo $methodfile exists
     newmethod=`cat $methodfile`
 else
     newmethod=$METHOD
 fi

 if [[ $newmethod != $method ]]
 then
     gconftool-2 --type string --set $OPTIONS $newmethod
     method=$newmethod
 fi

 gconftool-2 --type string --set $FILENAME $i

 sleep $SLEEP

 done
done