Sorry folks, I'm heading to bed and only just saw this post. I don't think religions in the Conan game use holy symbols like dnd does. But check out the story "Black Colossus" for descriptions of a bunch of gods. (The second chapter has princess Yasmela going to an idol of Mitra and praying to it, with a description of a shrine and sculpture of the god, with Vateesa saying, "This is but an emblem of the god. None pretends to know what Mitra looks like. This but represents him in idealized human form, as near perfection as the human mind can conceive. He does not inhabit this cold stone, as your preists tell you Ishtar does. He is everywhere - above us, and about us, and he dreams betimes in the high places among the stars. But here his being focuses."
This story goes into various gods to more or lesser extent. Also, "The God in the Bowl" goes into Mitra vs. Set more or less too. So the stories are the best sources of how different religions work. I put in a list of gods after a query from LokiOne in this thread: http://www.mongoosepublishing.com/phpBB2/viewtopic.php?p=85826&highlight=#85826. It has references to where I found mention of the god, but not spelled out. Maybe this would help? I didn't spell out the stories, but could if anyone wanted to know/cared.