You have a sun in the sky. If it should be night (it is dark, right?) then the sun should not be there  

18 hours ago, jbadams said:

That does sound like similar gameplay to Slender - perhaps you could take some lessons from the design of that game. 

If you're aiming to scare players, I'd pay particular attention to sound design, which can be very effective.

Nice analysis. Beside jump scares (i.e. zombie getting out of a closet), using out of place things to scare audience appears to be a common design element. For example, Stephen King used a clown character in his "It" novel: a clown may not look that scary in circus, but seeing a clown at night in the woods totally changes the perception. Although these new Alien games, very similar to Slenderman or OPs design, don't use it that much, yet still manage to scare many players. But Silent Hill, Penumbra and Amnesia do use it. A lot of people are scared of things they are bad at or when a game appears to know too much about them, so if you carefully analyze player, you can present experience that will genuinely scare him/her. Maybe trying to processing his Facebook profile and incorporating statistical findings into game experience, unknown to player. That will scare the crap of a typical player. Half-open spaces, like wood, where danger can come from any side, yet there are some obstacles that my hide the danger, seems to make player uncomfortable too. Slenderman games also use tall grass with small kid monster hidding in it. Children of the Corn has cornfields instead of wood, where hero moves through it, suddenly stumbling upon some sacrifice place.

Both Slenderman and the horror-based clowns exploit the psychological issues we commonly call the Uncanny Valley.  They are close to human, but exhibit features that are disturbingly not quite human.

Things being out of place causes tension for similar reasons: Players know that something should be a certain way, but it is not quite correct.

The effect only works while the material feels improper.  As an example, when the Dr Who franchise introduced the Weeping Angels they were creepy because the behavior was both human-like and disturbingly non-human, the same effect as the Uncanny Valley.  But as the series repeated the behavior over and over and over again viewers recognized the behavior as normal and typical for that creature. 

it takes a bit of skill and a bit of luck to find it, but there is a place where something looks and feels like it should be correct, but still has subtle not-quite-correct aspects that are disturbing and make the hairs on your neck stand up. Your brain recognizes that it isn't quite right, even though logically you could work past or excuse the differences.

18 minutes ago, frob said:

Both Slenderman and the horror-based clowns exploit the psychological issues we commonly call the Uncanny Valley.  They are close to human, but exhibit features that are disturbingly not quite human.

Stephen king uses it a lot, i.e. clowns, creepy children, or Pet Sematary's zombie cats, that appear normal at first. Although he also uses other fears, like acrophobia. The labyrinth environment could be unconfortable too, if there are a lot of pathways, with monsters setting up an ambush behind a corner, breaking ceiling behind player (Resident Evil 7 style). In fact, it is nice to study, how they changed everything from RE7, which is completely different from previous RE games, although actually returning to the Alone in the Dark roots.