Going through the Beta Site champion pages, plus a few of harrow's post (about multi-allegiances champions and about Sion's origin) I made a list about the Factions and it's champions:
About the factions:
There are currently 12 factions, plus the Independents.
Demacia, Noxus, Zaun, Piltover, Bandle City, Bilgewater, Ionia, Freljord being the City States recognized by the league.
Mt. Targon, Shadow Isles, Shurima and The Void being places where there weren't any cities, or are another dimension or something.
- I can't see Mt. Targon going for the City State status, too warlike, and the Solari too few.
- Shurima could have survivors, but Ezreal in Aatrox teasers said that there wasn't anything there.
- Shadow Isles could move politicaly and get recognition, but it wasn't stated in the Shadow Isles patch.
- The Void is the void, they don't realy care about politics and stuff, they do Void-stuff.
It's weird that the League itself isn't a faction, as champions as Ryze, Kayle, Taric, Malphite and the Prissioners were directly affiliated with it.
About the Champions in each factions:
- Fiora, Galio, Garen, Jarvan IV, Lux, Quinn, Shyvana, Vayne: Prety straightforward Demacian, all known, some of them like to shout their country's name around
- Poppy: She has ties with Bandle City.
- Sona: Is native Ionian, but is only listed as Demacian
- Taric And Kayle: Are Aliens, directly related to the league, why is he Demacian now?
- Xin Zhao: Now is listed as Ionian, well, he could hail from there, as it makes sense as he looks asian, and he had to be from somewhere before the Fleshing. We'll see.
- Darius, Draven, Katarina, LeBlanc, Swain, Talon, Vladimir, Cassiopeia: Standar Noxian fare, likes to kill stuff, some are part of a knife nut family, others part of a secret society of ancient secrets and magic, I guess that this could be added as a faction.
- Morgana: Alien with ties (if by ties you mean a Bakery) to Noxus. Is stated to be more independient.
- Urgot, Sion: Noxian warriors to the death and beyond, linked to Zaun, as in Urgot's case his rebirth was there, Urgot's link is listed as an error, let's see what's going to happen.
- Riven: Embraces Noxian ideals, but right now is opposed to it's leadership, I would list her as Independent.
- Blitzcrank, Twitch,Viktor,Zac: The general Zaunite, pretty diverse crowd, even though politicaly they are mostly independient, Blitz more to the league and Viktor to the GLORIOUS EVOLUTION but could work under Zaun. Zac and Twitch are more related to the city.
- Dr. Mundo,Singed,Warwick: They in some point were stated as noxus allies, does this still stand?
- Sion,Urgot: See Noxus
- Caitlyn, Ezreal,Jayce,Orianna,Vi: The peacemakers, the inventors, the invention and the archeologist. Orianna might seem the odd one out, but if she holds her father's and her.. namesake's wishes, she'll fight for Piltover.
- Corki,Heimerdinger: Shouldn't Ziggs be here as well?
- Zilean: What? He should be Independent (As Uristan only survivor, it doesn't need mediation), or tied to the league after the Kalamanda incident. I would see him in the Shurima crowd before here.
- Ziggs,Rumble,Teemo,Tristana: The Yordles with the interest of Bandle City at heart... are not many. Ziggs should be tied to Piltover as well, I think
- Corki, Heimerdinger, Kennen,Poppy: This is why Rumble feels the need to be a nationalist, too many Yordles are loyal to somewhere else before Bandle City.
- Amumu: I guess nominaly is a Bandle City champion, but there's nothing there for him he isn't even being driven mad by the issolation, should be either independient or tied with Shurima.
- Lulu, Veigar: Even if this is their birthplace, their morals don't align with it and don't care about it, they should be both independient.