linux - embed a bash script into the raspian for desktop background -

i want change default raspbian desktop background else. managed change splash screen want change desktop. splash code following here

do_start () {  /usr/bin/fbi -t 1 -noverbose -a /etc/splash.png     exit 0 }  case "$1" in   start|"")    do_start ;;  restart|reload|force-reload) echo "error: argument '$1' not supported" >&2 exit 3 ;; stop) # no-op ;; status) exit 0 ;; *) echo "usage: asplashscreen [start|stop]" >&2 exit 3 ;; esac  : 

any appreciated. thanks!

edit: want know how code works displaying background of desktop while booting system.