Keep in mind that society hasn't fully recovered from the apocalypse (to say the least), so society tends to be somewhere near the thin line between tribalism and feudalism. This is closer to the early Dark Ages than to the Age of Chivalry: things are chaotic, many roads (not to mention forests) are unsafe, and kingdoms resemble fragile alliances rather than centralized powers. The most powerful leader in the area usually gets to be king, with lesser leaders swearing fealty to him, and, in turn even weaker leaders swearing fealty to them. But this doesn't prevent them from fighting each other, and, if the king loses even a little bit of his power, some of his vassals are likely to try and grab the throne.
The majority of population has fled to the new fertile lands, and refugees from many cultures and races have settled in these areas. In these dark days necessity creates very strange bedfellows, such as goblin chiefs swearing fealty to a human king, or humans swearing fealty to a dragon lord. Anyhow, the starting barony would be human (with some dwarven and halfling settlements), neighboring an elven "barony" (actually a semi-tribal entity, with the tribal council swearing fealty to the king), and a hobgoblin barony. The king himself is human.
Nearby there is a dwarven kingdom ruling a few surviving mining-towns on the western slopes of the mountains (though the dwarf king has human vassals, too), a swampy area around the river where a water-fey (or water-nymph?) "rules" over (or, more accurately, advises to) a chaotic collection of lizardmen, fairies and treants, and a horde of all sorts of savage humanoids (orcs, kobolds, troglodytes, gnolls, trolls) and some other monsters ruled by some monster I haven't decided on yet (mind-flayer? dragon? high-level mage of some sort?).
Regarding religion, I haven't decided much yet, though I'd like to have more than one faith. It is still possible, especially in the fertile lands, to worship the warmer aspects of the Mother Goddess, though even then there would be a feral streak in the faith (which would be some kind of druidism). The Clockwork God has a cult, though I don't know how much of an inroad such an alien deity would make outside of the frozen lands. There would probably be other gods, and possibly a monotheistic faith.