Anything made by the government is copyrighted and cannot be copied until it is 50 years old. When it is 50 years old it can be copied by anyone. If things in Australia have not been published they are copyrighted. Things are not copyrighted if the person who made the thing has been dead for more than seventy years. If no one knows who made the thing it will not be copyrighted seventy years after it was published.
Here are some images that are not copyrighted from Australia: