The slide show screen saver is default and cannot be changed but you can change the backlight time so the the screen saver wont show
How Do I Change The Lock Screen Wallpaper On A Samsung Mythic?
It's super easy. Slide to whatever screen you want to change wallpaper then go into your settings or to your pictures and fin one to set as wallpaper then zoom in as you would like and set. This wallpaper will be set to whatever screen you were on while doing this.