Any decent library should have at least some of these books. As you know, Elm Hall was a sugar plantation, later becoming part of the Godchaux family holdings. You can go to Goggle Books and do a search for "Elm Hall Plantation" and you will get plenty of hits. I believe one of the books has a painting of Elm Hall as it appeared in its prime. Since the plantation survived until 1922, its likely there are photographs of it.
Little is left of the site but a couple of recent photos of the remains can be viewed at: