shell script before splash screen in pi - linux

Question

I have a raspberry pi running the Jessie OS, and would like to run a bash script to execute before it does anything else, such as the splash screen.
The shell script is a simple feh command because I want the pi to operate as a slideshow of images in a picture frame and nothing else; hence needing the pi to start the shell script immediately.
It would also be great if I could have the functionality to restart it if the shell script is exited for any reason.
I have tried cron jobs, /etc/init.d, and /etc/rc0.d, however, none of these have worked for me yet.
I have my main shell script in /home/imgs/slideshow.sh and then I run the following script to set things up to hopefully run as init.d:
#!/bin/bash
sudo apt-get update
sudo apt-get install feh
sudo apt-get install xscreensaver
sudo apt-get upgrade
# Make slideshow startup file in init.d if it doesn't exit
# if it does, make a backup file and rewrite it
FILE=/etc/init.d/slideshow.sh
if [ -f "$FILE" ]
then
sudo mv $FILE $FILE-backup-$(date +"%F-%T")
else
echo "$FILE does not exist but will be created"
fi
# input this text into the file
/bin/cat <<EOM >"$FILE"
#!/bin/sh -e
DAEMON="slideshow" #Command to run
daemon_OPT="" #arguments for your program
DAEMONUSER="user" #Program user
daemon_NAME="slideshow" #Program name (need to be identical to the executable).
PATH="/sbin:/bin:/usr/sbin:/usr/bin" #don't touch
test -x $DAEMON || exit 0
. /lib/lsb/init-functions
d_start () {
log_daemon_msg "Starting system $daemon_NAME Daemon"
start-stop-daemon --background --name $daemon_NAME --start --quiet --chuid $DAEMONUSER --exec $DAEMON -- $daemon_OPT
log_end_msg $?
}
d_stop () {
log_daemon_msg "Stopping system $daemon_NAME Daemon"
start-stop-daemon --name $daemon_NAME --stop --retry 5 --quiet --name $daemon_NAME
log_end_msg $?
}
case "$1" in
start|stop)
d_${1}
;;
restart|reload|force-reload)
d_stop
d_start
;;
force-stop)
d_stop
killall -q $daemon_NAME || true #replace with an apropriate killing method
sleep 2
killall -q -9 $daemon_NAME || true #replace with an apropriate killing method
;;
status)
status_of_proc "$daemon_NAME" "$DAEMON" "system-wide $daemon_NAME" && exit 0 || exit $?
;;
*)
echo "Usage: /etc/init.d/$daemon_NAME {start|stop|force-stop|restart|reload|force-reload|status}"
exit 1
;;
esac
exit 0
EOM
sudo chmod +x /etc/init.d/slideshow.sh
sudo chmod 0755 /etc/init.d/slideshow.sh
sudo chmod +x /home/pi/imgs/slideshow.sh
sudo chmod 0755 /home/pi/imgs/slideshow.sh
sudo systemctl daemon-reload
sudo update-rc.d slideshow.sh defaults