In a medium saucepan, bring pomegranate juice to a boil over high heat. Reduce heat to medium and simmer until juice is reduced to 1/2 cup, about 20 minutes. Stir in blueberries and simmer for 5 minutes longer. Transfer compote to a bowl and let cool.
In a medium dry saucepan, toast millet over medium heat, stirring, until millet begins popping, about 3 minutes. Stir in milk, vanilla bean, honey, cinnamon stick and salt. Bring mixture just to a boil. Reduce heat to low and simmer, covered, stirring occasionally, until millet is cooked through and mixture has thickened, about 25 minutes. (Millet will thicken further as it cools.)
Discard vanilla bean and cinnamon stick; spoon pudding into bowls. Top with compote; sprinkle with nuts, if desired. Refrigerate leftovers.