Phosh lockscreen/app-grid background customization

gtk.css

/*
 * ~/.config/gtk-3.0/gtk.css
 * Restart phosh using "sudo systemctl restart phosh"
 * Background image opacity is currently set to 30%. Decrease 0.7 values to increase background visibility.
 */

phosh-app-grid {
  background-image: linear-gradient(rgba(0, 0, 0, 0.7), rgba(0, 0, 0, 0.7)),
                    url('file:///home/lowkey/Pictures/background.jpg');
  background-size: cover;
  background-position: center;
}

phosh-lockscreen, .phosh-lockshield {
  background-image: linear-gradient(rgba(0, 0, 0, 0.7), rgba(0, 0, 0, 0.7)),
                    url('file:///home/lowkey/Pictures/background.jpg');
  background-size: cover;
  background-position: center;
}