wiki-knowledge often a good starting place, it will give you the basic knowledge you need to get started-- never a totally accurate resource
This site, however is a little more promising.
This site starts to get into the history of Voodoo and how it was a religion brought overseas by the movement of Africans to America through the slave trade. She mentions that "Nigeria and Dahomey" are two of the most common locations they were brought from. So that means I'll be looking into their cultures for some aesthetic clues for the set.
Here is an image of the royal bini mask from Nigeria. A well recognized traditional mask.
Here's a site with some interesting information about voodoo symbols: http://altreligion.about.com/od/symbols/ig/Vodoun-Veves/
And now let's take a look at Nigerian and Dahomey huts: The first and second are my favorites.
Not a bad start! But I'm going to hold off on doing too much more research until I get a chance to talk to the director. Who knows what they might actually be looking for.