How to stop photo shuffle on wallpaper

Enter Settings -> Wallpaper, or alternatively enter said setup from the lock screen (long press on wallpaper). You can then set up a new wallpaper that does not make use of photo shuffle, as as far as I am aware, you are currently unable to change the wallpaper type from "photo shuffle" to one single image.

Alternatively, in case that would be sufficient, you can change the shuffle frequency from whatever it is currently set to to "on tap", which will disable automatic shuffling, yet you may still change the wallpaper e.g. by accident.

Have a good day.