Religion and Alignment
In this world, there a few options as far as religion goes. First and perhaps most prominent is the Holy Church of the Eternal Light, a monotheistic religion (in theory) that reveres a being known variously as the Eternal Creator, the Light, the All-Mother, or simply God. Like all religions, there are splinter groups and sects within the church as a whole, such as the Wayfarers, a sect that focuses on the duality of light and dark, with a focus on the dark (they are not necessarily evil, though wayfarers can usually be described as unsettling at best). The church teaches that all other deities are false, a belief that does not endear them to followers of other faiths and they are often willing to force conversion to the true faith at swordpoint, though not all followers of the light are militant or rigid, and most are happy to leave peoples with faiths different from theirs believe what they will. The least aggressive of them are, ironically, the Wayfarers - they believe that the nature of the light and dark is vast enough to encompass all things, and that all creation is an expression of the creators will.
Next is simple nature-worship, an animistic faith whose adherents believe that there are spirits which govern every single thing in creation. Many people in more rural areas as well as elves and the Shou humans venerate nature and the spirits, an ancient practice that predates the existence of the Light as a religion and is mostly informal.
In the burning deserts of the south, the dark-skinned people there venerate the powerful and near-godlike Djinn Lords that rule those lands, and their priests are as often sorcerers as they are clerics or paladins, paying them tribute in treasure and slaves.
Race by Race
Humans can follow any faith, depending on their inclinations and culture. the Shou generally tend to be nature-worshippers, and more humans than any other race are followers of the light.
Dragonborn - the dragon-kin usually worship no deity, believeing only in their own strength and prowess to make their way in the world, but those who choose to join a faith tend to be some of its most fanatical adherents.
Dwarf - Dwarves are split along genetic lines when it comes to religion. The mountain dwarves of the frozen north are devout followers of the Light, whilst the more nomadic Hill Dwarves have diverse ranges of beliefs based on their culture and personal inclinations.
Elf - Most elves venerate the spirits of nature, though a few have found peace and purpose as followers of the Light (or dark, in the case of the Drow).
Gnome - You will be hard-pressed to find a gnome that does not revere the spirits of nature.
Halfling - Halflings who bother with religion at all usually pray to the spirits of nature, but the Stout halflings of the south worship the Djinn just as all other people there do.
Half-Elf - Like their human and elven parents, they follow whichever faith their culture or personal inclinations dictate.
Half-Orc - Half-orcs raised among humans have as diverse a range of religious beliefs as their human parents, whilst those raised among orcs tend to venerate the spirits of nature like their orc kin.
Tiefling - Tieflings have no particular religious inclinations, though they are slightly drawn toward the Holy Light. Tieflings who venerate the djinn are virtually non-existent, as tieflings found in the southern lands are typically killed on sight or at birth.
Alignment works a little differently in this universe. Firstly, the Good and Evil alignments are replaced with Light and Dark. Chaotic and Lawful remain the same, but they represent something different - Lawfully-aligned souls are strongly associated with order and stasis, while chaotically-aligned souls favor entropy, the universal force of destruction that breaks down all things. Your characters alignment is not an expression of his or her personal ethos or actions so much as it is simply the way in which your soul is inherently aligned. A persons alignment is set at birth, and nothing short of powerful magic can alter it. Many a good persons soul is aligned with the Dark through no fault of their own, and even the most black-hearted villain can have a soul of purest Light. in this world, you must play the hand you are dealt. Your souls alignment may incline you toward dark, light, law, or chaos, but what this means is that even if you can somehow find a way of discerning a persons alignment, there is no guarantee their alignment will be an indicator of the type of person they might be. the degree to which a persons alignment affects personality varies wildly from individual to individual.
If anyone wants to change their alignment or character background as a result of this, feel free. From a mechanics standpoint, divine characters can freely choose their oaths/domains/etc as fits their belief system. PC paladins must carefully delineate what oaths they took upon reaching level 3.