Well I know Tanya's stand on the subject. What I want to know is whether it's also the author's. I don't know about the LN and manga or interviews, but as far as the anime goes it could be interpreted both ways: the author showing that whether one believes in god or not god still exists, or the author shitting on religious nuts by self-inserting as Tanya. I ask because the artist of the OP pic is a religious nut, and he's a big fan of the series.
I myself am an atheist who is writing a story about a detective who don't believe in the supernatural. She solves mysteries with logical deductions (e.g. there's no vengeful ghost, the victim was murdered by a human who made it look like it's a supernatural phenomenon). But at the end, I like to add a scene where the victim's ghost thanking the detective who didn't know she exists. So I definitely can see similar fiction creators who like to portray gods/supernaturals existence even if they don't believe it themselves. I'd laugh my ass off if a supertitious fool admire my work because they mistakenly think I'm fighting for their cause.