These will overlap with religious views but don't take offence at the label of fictional. The observable universe so far is one thing but what we believe or used to believe is still of importance to our lives and cultures. The story of our understanding of the universe is incredibly interesting and this is partially the result of our collective thoughts over thousands of years.
The universes noted below are those that can be freely chosen for writing a text, although they are more likely to be chosen for fantasy, science fiction, romance, paranormal and horror texts than any other sort.
The flat world in an unobserved universe
This world in the be all and end all of existence and the universe surrounding it almost like a painting or kaleidoscope in importance. The revolutionaries of this world will take note of the as yet unobserved universe but most will simply be enchanted by the sight of it only. Otherwise, life revolves around daily events and the importance of things with immediate consequences (few will be thinking in terms of centuries or global events). The universe may be extremely limited but it does offer an opportunity for its inhabitants to be greatly shocked by an encounter with something other from another part of the universe, being it a living being or otherwise. Also, this universe offers an opportunity to focus intensely upon the minute events and reactions and build them up as representatives of greater events in reality.
The three-four layer universe where navigation is based on life, death and your actions
Commonly referred to as Heaven, Earth, Purgatory (often left out nowadays) and Hell. For the purposes of fiction this universe is often restricted in the living world to just Earth and extended in the death-based worlds to overlapping or layered eternities. This universe structure contains beings of non-human origin and great power who often control, enslave, manipulate, ignore or care for humans. On top of that, there are some stereotypical experiences the dead will have to go through although these experiences can be manipulated in fiction or written out entirely. Common mode of travel is a portal like transfer, either a white one or a fiery one. The most uncommon mode of travel is to Purgatory and is often explained as a fading from existence as going to Purgatory is essentially to become lost to the world and the other destination. This universe is useful for moralistic stories and for the inclusion of certain types of monsters and creatures.