This is Bayou Des Famillies outside New Orleans. The Twenty Oaks swamp would be similar, but darker and more confined.
The exterior of a plantation called Madewood. Twenty Oaks would not be as well kept as this, but it does show the grandeur of the old south. Just imagine it shaded by a huge old willow tree.
The formal dining room of Madewood. Drape the furniture and add an inch or so of dust and the Twenty Oaks ballroom would look a lot like this.
A second floor hallway in Madewood Twenty Oaks' second floor?
Crypts from St. James and Louisville No. 1. The Lafayetteville Old Cemetery crypts would look much like this. In some places crypts are so badly weathered it is possible to look inside. If you happen to be doing a little research...

Jossie's golden silk spiders. At certain times of year, the swamps around New Orleans are thick with these creatures. It's probably a good idea not to scare them.
This is no froggie...
Dwarf Palmettos grow in great profusion on swamp floors around New Orleans. Here's a swamp near Bayou Coquilles which looks pretty much like Jossie's. All you have to imagine is heat, humidity, mosquitoes and maa-maa beasts.
This roadhouse north of New Orleans has seen better days. Enlarge the front window, add a sign and an overgrown field and we have Christabel's.
Intricate scrollwork similar to that found over the Twenty Oaks gate.
A voodoo shrine from a private museum in New Orleans' French Quarter. Prudence's shrine would have incorporated some of these elements. Much taller candles, though.
The slave cabins of Laurel Valley north of New Orleans have been restored for the tourist trade. The shanty town occupied by Lusanne Linton, Sarah Lee and Youngjohn Amos would look much like this. If we improved on the swamp, that is. Say black water and a brooding forest of tupelo and cypress.