In my current (Phase 2) playtest of Volant, the players created a religion for their characters, called Luminism. It is a dualist religion - there are two goddesses, one of Light (Luma), whose symbol is the sun, the other of Dark (Hera), whose symbol is the moon. They are the only two gods in the world, and all other gods are views of one or the other, or sometimes odd blends of both. Luma constantly strives to raise up humanity into the Light of knowledge, reason, kindness, and mutual respect, while Hera strives just as hard to keep humanity in the Dark of ignorance, diabolism, hatred, and suspicion. Luminism's theme is that these people are the Chosen, who can see beyond the veil and detect the machinations of Hera and the blessings of Luma.
The organization is very democratic - priests rise according to their popularity. The influence of the faith is national - most everyone in the nation pays at least lip service to it. It has one major taboo - having sex with only one person at a time - as they are currently in a nation where everyone has sex in massive orgies, and no child knows who his or her father is, this is rather important. There is also one important ritual, the taking of a ceremonial glass of wine at noon every day, in communion with Luma. This communion is of vital importance in play, for it determines who is a Practitioner - one who takes communion only when convenient, who is a Believer - one who takes communion even when convenient, and who is a Strong Believer - one who takes communion at noon, even when it is dangerous. Worship, aside from the daily communion, is held in a Temple with many others. Heresy is tolerated, but not welcome. Every effort is made to reunite schismatics with the body of faithful.
The duties of the faithful are adherence to the daily Communion ritual, along with prayers, and the sacrifice of a goat on the four High Holy Days - Midwinter, with fasting and vigils; Midsummer, with feasting ans celebration; and the two Equinoxes - spring brings cleansing and renewal, while autumn requires repair and preparation. The Holy Sacraments are Age of Consent, when a boy becomes a man and a girl becomes a woman, Marriage, and Death.
All of the paraphernalia are used in worship - reading Holy Books; Incense in the temple worship; Icons in the temple and the home; Ritual Implements used by the priests in blessing the people and projects under their protection, as well as forcasting the will of Luma; Special Clothing worn by the priests to distinguish them form lay people, red scullcaps and stoles over white tunics; Music played and sung in the temples and home; Candles lit on the High Holy Days, as well as in remembrance of the dead; Jewelry worn by worshipers, a golden sun worn as a pendant, earrings, or pin; Dance in the temples on the High Holy Days; and clockwork Devices in the temples, designed to amplify the music and voices, to split the sun's light into prismatic displays, and to waft incense over the congregation.
The PCs all belong to a religious order of knights, who are dedicated to furthering the designs of Luma, wherever they need to be. The campaign *really* picked up steam when their religion came into it strongly, and the ranking Strong Believer had to make religious decisions based on his reading of Luma's will - which entailed placing certain people in this new land under the Ban - from the Old Testament, the term means the ritual slaughtering of everyone - man, woman, children, puppies, kittens, and birds - subject to the Ban. They have already killed entire households, bands of Special Police, and even enemies who have surrendered. Miracles have occurred, and none in the party doubt their path. So far, it's been a very interesting campaign! :D