I can't find any topic about that but for this sort of game is very important to have guilds like thieves, merchants, assassines, mages. Player could have some interesting informations from them, special items and abilities, but belonging to guild would require devotion for example - being caught on stealing - and you're thrown out from merchants guild.
Another thing is religion and beliefs, you could choose your own God and sacrifice for it items and animals, to have blessings, also philosophical quasi guilds like in Planescape Torment would be nice.