Spookilicious Mama, I will suggest a
Masquerade party based on the Venetian Carnival theme. You know with all the guest dressed up in black with masks, kind of like in the Kubrick's
Eyes Wide Shut movie ?
(see that link if you don't know what I'm referring to :
It looks very classy, such as a upper class like party, and very creepy too! All those expressionless mask gathered... Maybe you could add some Italian opera, or baroque music playing while the guest are chatting and having some fun. Feel free to improve !