Changing Wallpapers in Moto G5 Plus can be done by following these steps, from your home screen long press where you can see three options – Wallpapers, Widgets and Settings.
Tap on Wallpapers which will take you to another screen with options like Live Wallpapers, Photos and Wallpapers.
Though there are no default Live Wallpapers you can install a separate app for this. By selecting photos which will take you to the gallery where you can select one. When you click on Wallpapers it will prompt for installing a Wallpaper app, this is a very good app with beautiful wallpapers with different categories.
Couple of best Live Wallpapers from the play store are Mush rooms 3D Live Wallpaper and Koi Free Live Wallpaper.