Well Purgatory is where “monsters” go when they die it hasn’t really been well defined. The writers have a lot of leeway with who could show up there.
Bobby: Rejected his reaper and had the boys kill his ghost self.
John and Mary Winchester: Mary was last seen as a ghost and John as a glowy spirit. Current location unknown.
Jo and Ellen: Super bamf of heaven Ash knew the second Dean and Sam arrived in heaven but wasn’t aware that Jo and Ellen were even dead. Jo was last scene as a vengeful spirit (sort of). Souls unaccounted for.
Madison: Sam’s werewolf love from Heart. Chose to sacrifice herself but still a werewolf, so you know.
Agent Henricksen, Meg Marsters (Human), Ronald: Raised during the rising of the witnesses, last seen as vengeful spirits before being vanquished by Dean, Sam and Bobby.
Angels? ANGELS: Gabriel, Balthazar, Anna, Uriel, Raphael …the rest. Time for an awkward family reunion.
Demons? DEMONS: Azazel, Lilith, Ruby, Alastair, and every other demon we have ever seen die, should be in Purgatory.
The Psychic Kids: They all had the demon blood in them so maybe we could see Ava, Jake and Andy (especially Andy) again.
Corbett: He’s probably still haunting Ed but you never know.
Amy Pond: She was a monster with a heart of gold and Dean knifed her. She could punch him in the face.
Dean’s monster daughter: Or we could forget this ever happened. Either way.
Bela?: Should be a demon by now. Maybe the boys killed her without even knowing it.
Every monster/ghost/demon the boys have ever killed: Have fun Dean.
Edited to add:
Gordon Walker: How could I forget that crazy mofo hunter who died a vampire.
Lenore: The good vampire that Sam and Dean saved from Gordon only to have her come back in season 6 to be randomly killed by Cas for some reason. The rising of the Alpha vampire made her really hungry or something?

sam
does your badge say that you’re special agent han solo
Guys look at number 33 and 34.
3 of the avengers and the Winchesters are on this.
This was obviously made in a moment of deep inebriation and after getting dumped
cackled like a lunatic at #1
A’capella cover, huh… we’ll see about th… …
