Depending on your preferences, you can use whatever type of bread you choose. The heartier the bread, the more filling the casserole. Crusty French or Italian bread works well. The blueberries can be substituted for any type of fresh fruit. Apples and chopped nuts would be really good. Also, if you would like your French toast casserole to have more of a bread pudding texture and not be as crusty, decrease the cooking time by 10 minutes. Check to make sure the center has set up and is not runny.