So for people who we can be pretty sure are not the White Walker, we have:
gimmepie
Seth Rollins
apocalypseArisen
Mana
Nakuzami
Charlie Brown
eros (provided Nakuzami is correct0
Candy (if it's true that Charlie Brown was converted to a wight, then he can't state who the WW is or vote for them)
Still wanna see how things play out though, so I'll table my vote until more info comes to light.
I'd argue that there's more than that as well - so far into the game I'm sure most house members are aware of who else is in their house PLUS have this list that everyone can use as well. Further narrowing it down. :)
Now mind you, if a person is just a peasant with no loyalties declared, then this list is all they got (unless they took notes of which people are sending subtle hints to others and can map out all the houses like that).
edit: And there's more than one conversion role guys - don't forget. There is still Lady Stoneheart too.
edit2: Wait, Soph... how do we know aA isn't WW? Did I miss something in an event that identified who aA is playing as? O:
wait why was i quoted. I actually remember that much, just that no one really seemed to have direction yesterday.
Though not related to the WW Naku got info from the greenseer does this mean potentially four others got information from them as well?
eros is an unaffiliated role within House Stark.