By no means do you have to stick with these topping ideas! Use whatever fruits are in season, whatever nuts you like, whatever seeds you can tolerate.
I know I sliced the nectarines in the picture, but chopped makes much more sense for even distribution with the barley.
You can leave out the maple syrup drizzled on the top if you want. You can also use brown sugar or agave to sweeten. And if you're okay with this not being vegan, honey or sweetened condensed milk works well.