My World of Cinder uses the primordial 3 alignment system of Law/Neutrality/Chaos and the three main religions fall out roughly along those lines.
The Church of the Gold Dragon
Alignments: Lawful, Neutral.
There are no good/metallic dragons in the World of Cinder, only neutral and chaotic ones. The Church of the Gold Dragon is basically the Crystal Dragon Jesus trope taken to its illogical conclusion. I don't normally use this kind of faux medieval Christianity in my games, but I'm trying to step beyond my normal Howard-esque sword & sorcery roots to allow for pious knights and clerics and grailquests and all that sort of Arthurian stuff. But the Church isn't all gumdrops and lollipops. The faith supports the social classes of early feudalism, going so far as to divide its sacred texts into Copper, Brass, Silver, and Gold Codices. Only the Copper Codex is used in the presence of the peasantry. Nobles are given access to the revelations of the Brass Codex. The Silver Codex is reserved for clerics. Only the Patriarchs of the Church may read from the Codex of Gold.
Your basic Greek/Norse/Kirby New Gods mash-up pantheon with a Mother Earth and a Father Sky and a sea god and all that standard stuff. Not necessarily opposed to the Church of the Gold Dragon, but open conflict between the two is certainly possible. The priests of the Twelve are losing ground in the long, slow competition for faithful followers, as the Church is better organized and the chaotic dudes (below) promise quicker results and more fun. Some priests of the Twelve are getting all apocalyptic on everyone's asses, claiming that falling away from the Old Faith will only hasten the end of the world.
The Frog God Cults
Alignments: Neutral, Chaotic
Slaad worshippers. Chaos cultists in the tradition of Warhammer. Dudes in black robes wielding wavy-bladed daggers. Naked witches. Etc. In some areas a Frog God might be worshipped openly, but in many regions this faith has gone underground. The Frog Gods are not necessarily evil, but they are opposed to many of the institutions of Cinder society. And their propensity for human sacrifice puts them outside the law in many areas. Totally metal.
Those are the three main faiths of the land. Jesus is a dragon, Satan is a frog, and Thor still speaks crazy faux English. Other religons exist, such as localized mystery cults with weird initiations, heretical off-shoots from the Church, the odd non-amphibious chaos cult, and minority cultural groups with their own secretive ways.