Randomize GNOME3 Wallpaper

I've been looking for a simple script to randomize the display of my wallpaper on my GNOME3 desktop.  After trying a few apps and not finding anything satisfying, I made my own. It's based on Dhananjay Sathe's wp-show but stripped of the GTK options dialog and some senseless redundancy.

Here it is:

#!/bin/bash
# To change wallpaper automatically after N minutes, add this to your CRON (where N is minutes): N 0 * * * /path/to/wp-show
base="/home/pluc/.walls/"
photo=$(find $base -regex ".*\([jJ][pP][gG]\|[jJ][pP][eE][gG]\|[gG][iI][fF]\|[pP][nN][gG]\|[bB][mM][pP]\)$"  -type f | while read x; do echo "`expr $RANDOM % 1000`:$x"; done | sort -n | sed 's/[0-9]*://' | head -1)
uri="file://"$photo
gsettings set org.gnome.desktop.background picture-uri "$uri"