First - Yes I took pictures, have not developed them yet. I am a skeptic about 99.5482% of all ghost photos I see. Most are hoaxes or can be explained by reflective light. --- But if I get anything I'll let you know.
As for the mass graves-- The Savannah you see today is not the way it use to look. The city has burned down a few times. The squares have always been there, but the function of the squares has changed. -- Some were markets, some were for laundry, some were for black smiths. Some were even used as grave sites and some for executions.
Savannah was hit by yellow fever more then once. Each time they simply dug mass graves and piled in body over body, dumping lime on them. Even the one grave yard left in view in down town has layers of bodies on bodies from Yellow fever.
Savannah has many old grave sites right on down town that were forgotten and built over -- only to be found years later. The old sites are marked with a simple stone. --- The people of Savannah are sure they do not know of all the dead under their city. The keep finding more.