I think it's much harder to do any special thematic chapters/events for a novel, compared to comics. Feels like it takes away too much from the original plot you're telling, and unless it's planned super well, it could come off like a weird commercial break in the middle of the climax.
On top of that, my series is an Isekai, so I haven't decided yet just how something like Halloween would translate to this other world, or if holidays like that might be a sort of cultural impact the main character has on the world, or at least on those around him...
