In medium mixing bowl or plastic container with lid, combine kefir, milk and oats; stir until well combined. Add in remaining ingredients reserving about 2 tablespoons of the nuts and 1 tablespoon of the maple syrup for garnishing. Cover and refrigerate overnight or at least 8 hours. When ready to serve, place approximately half the banana slices in the bottom of serving glasses or bowls, divide oat mixture evenly between them. Top with remaining banana slices, pecans and drizzle of maple syrup.