When I first realized there were a few "digging", "unearthing", and "buried" references, I first thought: an Undertaker type as an icon. Someone else mentioned a Grave Digger later on but it did not result in confirmations or much furhter talk.
The second thing I thought of was indian burial grounds. This was brought up in the last age (I think by Christy). Poltergeist is based off building a house on burial grounds and so the Victorian Mansion connection was made.
Then I also thought of old movie scenes of zombies coming out of their graves.
But I still think there is more to it. It might not be worth straining the brains anymore since the full reveal is this week...but its been a week already that I've been battling with these references.