1) Spread the bread cubes on a cookie sheet or other large pan to dry out for about an hour.
2) Whisk together the eggs, milk, salt, sugar, vanilla, cinnamon, and nutmeg.
3) If you're adding the bacon or sausage, arrange half the bread cubes in a lightly greased 9" x 13" pan, or similar-sized casserole dish. If you're not using any meat, place all of the bread cubes in the pan or casserole dish.
4) If you're using the meat, scatter it over the bread, and cover with the remaining bread cubes.
5) Pour the egg/milk mixture over the bread in the pan, pushing down on the bread to submerge it as much as possible.
6) Cover with plastic wrap, and refrigerate for several hours, or overnight.
7) Next day, preheat the oven to 350°F.
8) Sprinkle the top of the casserole with cinnamon-sugar, if desired. Bake for 60 to 70 minutes, until a toothpick or cake tester inserted in the center comes out clean, and the top is lightly browned.
9) Remove from the oven, and dust with cinnamon sugar, if desired.
10) Serve warm, cut in squares and drizzled with maple syrup, if desired.