I'm always up for more options to any given part of this game, and more beliefs is definitely something I'd love. For now, here are some basic ideas for Pantheon beliefs that haven't been suggested yet, since there are some deity types that aren't represented:
Goddess of the Moon- Naturally, the inclination for this belief would be to be the opposite of "God of the Sun". But not sure what would be the opposite of Granary and Wheat farms, while still remaining useful and not overlapping other beliefs... So perhaps, in reference to the lunar cycle and the moon's connotation with sorcery, this belief gives a large sum of

and a single random yield (which can be

,

,

,

, and

each cycle) every other turn? And seeing how the full moon is often associated with insanity, perhaps this belief causes

? Could make for a neat "risk and reward" strat: you get large sums of yields every few turns or so, but have to deal with extra unhappiness, but balance is hardly my niche. Just an idea guy
God of Storms- There's hardly a Pantheon that lacks a storm god, so why not? And I'm thinking perhaps this belief could reward pillaging, to reflect the sort of devastation storms and natural disasters leave behind. As a bonus, Denmark (the "Viking Civ") is all about pillaging, and who is the most famous god of the Norse pantheon?
God of the Dead- Another recurring "god type" in real-world Pantheons. But admittedly, it's hard to come up with how this belief would work... Can't do "kill units" cause that's God of War. Gain yields for your own units getting killed? Overlaps with Ceremonial Burial, and that'd be rewarding failure! And possibly exploitable. Perhaps losing a population from starvation? Again, rewarding something you
don't want to do. But then again, I guess that could be the point: doing something you normally wouldn't want to do for a potentially big reward. I'm afraid I'm stumped on this one, but listing it cause, again, every pantheon has a death/underworld god
Goddess of Time/Fate- Another type of deity present in almost all pantheons but not in here. But also a challenging one to figure out how to work... What I'm conceptualizing right now is maybe the ultimate snowball pantheon belief, wherein the yield gain and other bonuses get stronger with time. In this case, perhaps it grants +1 of all yields (

,

, and

, perhaps more) for the first few turns, and after 10-15 (maybe even 20+) turns or so, it becomes +2, and so on. And suffice to say, it scales with Era. But that's just an idea for how this belief could work, nothing concrete. Would be apt for this sort of belief to be powerful, of course, considering nothing can hope to defeat fate or time. But that's assuming, of course, that the Civ with this belief could stand the test of time