Butter a 9 X 13 inch baking dish. Cut twenty one inch slices from baguette and arrange in one layer in baking dish.
In a large bowl whisk together eggs, milk, nutmeg, vanilla and 3/4 cup brown sugar and pour evenly over bread. Chill mixture, covered, until all liquid is absorbed by bread, at least 8 hours and up to a day.
Preheat oven to 350. In a shallow pan spread pecans evenly and toast in middle of oven until fragrant, about 8 minutes.
Increase oven temp to 400. Sprinkle pecans and blueberries evenly over bread misture. Cut 1/2 stick butter into pieces and in a small sauce pan heat with remaining 1/4 cup brown sugar, stirring, until butter is melted. Drizzle butter mixture over bread and bake mixture 20 minutes, or until any liquid from blueberries is bubbling.