Grease a 9x13-inch baking dish with butter or cooking spray. Spread half of the bread cubes in the bottom of the dish.
Scatter the cream cheese cubes evenly over the bread, then sprinkle with 1 cup of blueberries. Top with remaining bread cubes and remaining blueberries.
In a large bowl, whisk together eggs, milk, maple syrup, vanilla, cinnamon, and salt until well combined.
Pour the egg mixture evenly over the bread, pressing down gently to ensure all bread is soaked. Cover with foil and refrigerate overnight (or at least 4 hours).
To freeze: After assembling, wrap tightly with plastic wrap then aluminum foil. Freeze for up to 2 months. Thaw overnight in refrigerator before baking.
When ready to bake, preheat oven to 350°F. Bake covered for 30 minutes, then remove foil and bake an additional 15 minutes until golden and set in the center.
Let stand 5 minutes before serving. Drizzle with extra maple syrup if desired!