Asking Captain Lonely-Gale about the prominent citizens of Windhelm will normally net the following response:
"There's an author named Adonato staying at the inn. He's published a few works of historical fiction. The clans Shatter-Shield and Cruel-Sea see most of the gold that passes through the city. And obviously you have Ulfric, the jarl and future High King. Oh, and that busybody Viola Giordano. She's got her nose in everyone's business, which I guess is one way of being prominent."
Vanilla already has a GetDead check for Viola, but not for the other people mentioned here. In addition, USKP added an alternate version of this reply that would omit the mention of Ulfric if the Empire controls Windhelm. However, there is still no check for Adonato being alive. The description of the clans Shatter-Shield and Cruel-Sea is pretty vague, but I would suggest adding checks for Torbjorn and Torsten. I think it is fair to say that the influence of these families would dwindle if their patriarchs get killed.