You can use any variety of or combination of nuts in this recipe. Almonds tend to be more affordable, and raw nuts in pieces (not whole) will always save you a couple bucks. I used a mix of almonds and walnuts to balance the hazelnut in the milk.
For variations, you could use all hazelnuts to create an even stronger Nutella flavor. Or, try Sweetened Vanilla Almond Milk and add white chocolate chips and dried cranberries.