feh and crontab 

Create file in /usr/local/bin, name it wallpaper.sh
Edit in:

#!/bin/sh
WALLPAPERS="/mnt/path/to/wallpapers"
ALIST=( `ls -w1 $WALLPAPERS` )
RANGE=${#ALIST[*]}
SHOW=$(( $RANDOM % $RANGE ))
feh --bg-scale $WALLPAPERS/${ALIST[$SHOW]}

chmod +x wallpaper.sh

Then use crontab-e
This one will change wallpaper every 5 mins


*/5 * * * * DISPLAY=:0.0 /usr/local/bin/wallpaper.sh