And then there is all the ways you could change up the nature of the cosmology itself. Most RPGs, particularly medieval RPGs, follow the Dungeons and Dragons setup of creating a polytheistic world and assuming that this polytheistic viewpoint is correct. No game has ever attempted to change things up on that front really, which is especially egregious for medieval fantasy games because the region and time period they are ostensibly based on was
monotheistic in belief, and the culture of the societies they portray is generally a medieval Christian society in all the important ways except the Christianity, even though it doesn't make sense for it to function that way, but the settings don't really do much with the polytheistic setup they've created.
It may do better to move away from the polytheistic cosmology and change things up. For example, having the main setting be monotheistic and having the monotheistic viewpoint be correct. "Pagans" worship other gods, but those "gods" aren't gods at all, but demons who lead people astray to chase false idols and cause mankind to lose faith in the one true God. This idea actually comes from the Bible itself, and was downright copied by
Paradise Lost. You could also have actual "devil worshippers" who outright get the most depraved abilities, in addition to the followers of false religions that get abilities from their "gods".
If you want to keep the polytheism, but don't want to do the same old thing, you could change up the polytheistic nature of the setting itself. For example, most RPG settings with religion, like Dungeons and Dragons, take a hard polytheistic stance. In hard polytheism, the "gods are distinct, separate, real divine beings, rather than psychological archetypes or personifications of natural forces. Hard polytheists reject the idea that "all gods are one essential god" and may also reject the existence of gods outside their own pantheon altogether." A setting could instead have a "soft" polytheistic stance instead, where the "different gods may either be psychological archetypes personifications of natural forces, or as being one essential god interpreted though the lenses of different cultures (e.x. Odin, Zeus, and Indra all being the same god as interpreted by Germanic, Greek, and Indic peoples respectively) – known as omnitheism. In this way, gods may be interchangeable for one another across cultures."
If you want to mix the Monotheism with the Polytheism, so you could have a medieval Europe analogue with a Christian analogue, while still allowing for other religions in your world, you could have the main society follow Henotheism, whereby there is the worship of a single, supreme god, but the existence or possible existence of other deities is not denied. Zoroastrianism was a famous real world example of this. You could also have the setting follow Monolatry, whereby there is the belief in the existence of many gods, but with the consistent worship of only one deity. Or, if you want to get even more esoteric, you could have the main setting follow Kathenotheism, where there is a succession of supreme gods, but you only worship one god at a time, with each deity treated supreme in turn.
Of course, if you want to downplay the role of God or gods in your setting, you could make your setting pantheistic, so that creation and the cosmos itself is god, or you could make your setting Panentheistic, where the divine is part of the universe, but also extends outside the universe, Note, that this is mainly about how your setting cosmology actually works; you could have different societies still have their own gods, and even have clerics or shamans who have spells, but these spells are given based on their personal faith, not based on a personal relationship with a god.
If you want to get even more esoteric, you could make you setting's cosmology autotheistic, which would hold the belief that " divinity, whether also external or not, is inherently within 'oneself' and that one has the ability to become godlike." Buddhism and Jainism are real life examples of this form of theism. This doesn't have to be as egoistic as it sounds, and it could allow clerics of every faith to power their magic from their "god", when it really comes from divine power within them.
And, finally:
There wouldn't be atheists or agnostics.
In a setting with open divine power, there couldn't be agnostics, since everyone knows that God or gods exist. Same with atheism. But, non-theism, a simple lack of belief in belief in God or gods, would still exists. You may have those who acknowledge that God/gods exists, but simply refuse to worship him/them, or show a lack of interest in doing so. You could have people who follow misotheism, and profess actual hatred for God or gods in the setting, or those who are maltheist, believing that the divine powers exist, but are wholly malicious towards man. You could also have people who follow Dystheism, believing that the divine powers are not necessarily wholly good, but may be considered evil. If you want to go hardcore, you could have one of these negative beliefs be wholly correct.
