One of the most ubiquitous of these visual cliches is a set where gore and filth cover as many surfaces as possible -- walls, floors, ceilings, furniture, fixtures, you name it. The idea is to gross out the audience, rather than to create a frightening or disturbing atmosphere, but even that attempt fails.
Let's review some examples first and then explore what is so off about the approach. In movies, the style began with Saw in 2004, although it appears to have made the jump from video games of the survival horror genre, such as Silent Hill 2 from 2001. At any rate, it continues in both media through today.
The Cabin in the Woods
Dementium: The Ward
The Evil Within
A Nightmare on Elm Street
Silent Hill 2
Silent Hill 2
First, it's information overload. There are simply too many details to attend to, across the entirety of the frame. Worse, there's no pay-off to inspecting them, as though one of the details held some plot clue or revealed something about someone's personality. The result is to leave the viewer confused, frustrated, and annoyed -- but not disturbed or afraid.
It also prevents tension from building in what is supposed to be a frightening scene. While your eye is busy scanning through all of those details on the walls, floor, ceiling -- everywhere -- it doesn't get a chance to rest. Tension cannot escalate except from an initial resting state (sparse details, silence, minimal action).
Nor can a surfeit of gory details represent an emotional climax, if it doesn't follow a period of tension-building. The approach is trying to blow us away with too much too soon -- we aren't awed but, again, puzzled about how the hell the scene got to look that way. And with so many details, no one of them stands out to grab our attention. Each bit of gore is only a drop in the bucket, as it were.
And although the intention is to portray a gritty naturalism, the overly filthy and gory surfaces strike us as incredibly unnatural. No dirty / abandoned / squatted place has so many sources of filth continually renewing the filthy look. Over time organic matter decays, so a long-abandoned bathroom will not have copious stains from urine, feces, or vomit. Blood dries and decays too -- are we to believe that every one of the myriad blood stains are fresh, without having seen them made? Decay of building materials is more likely, but most of that is structural rather than chemical -- stuff breaks down into smaller pieces, not discolored (as though every building material and fixture corroded like cheap rusty nails). Airflow blows dirt off the walls to settle on the ground.
Aside from how recently all these stains would had to have been made, there's also the matter of how they could've gotten to where they ended up. What source and path could have led to the placement that we see? Copious blood stains high on a wall or ceiling? Filth and grime dripping down a wall with no source above? When every stain is a mystery stain, the whole thing feels made-up. It strikes us as staged and therefore fake, reminding us that it's the result of deliberate and exaggerated set design. It's as though one of those shabby chic decorators was asked to apply their overly distressed style to a horror geek's bathroom.
Thus, the approach to gross us out fails because our disgust reflex is not triggered when we aren't convinced that we're seeing a plausible scene of gore and filth. It doesn't have to look 100% realistic, but it does have to feel plausible, and we don't feel convinced when it looks like some set decorator let loose with a gore-hose over every square inch of every surface.
Contrast the filthily encrusted look of contempo horror with the restrained or sometimes clean sets in classics from the late '60s through the early '90s. Really the only filthy shot is a close-up of a toilet in Candyman, but the establishing shot of the entire bathroom shows no gore, and not even that much filth -- more graffiti and trash than anything.
The Texas Chainsaw Massacre
Night of the Living Dead
With less cluttered surfaces, and only the occasional splotch of blood or filth, all of the problems are solved. There's no information overload, and we can start off in a resting state to build tension toward a climax. If that climax produces gore, there won't be that much since it comes from a single event, and we'll have seen its source and path, making its residue on the walls, floor, etc. believable and unobtrusive.
Fairly stain-free surfaces are also more what we see in everyday life, even when the place has been subject to weird, violent, and disgusting events. This relatively cleaner-looking set lends a naturalism to a story that is beyond the ordinary -- demonic possession, butchering, and the like. What truly disturbs us is the sense that something so bizarre could take place in our ordinary settings.
The restrained approach to set design not only succeeds in creating a disturbing atmosphere, it even succeeds at the goal of grossing out the audience, since we can focus better on the gross-out event, its source is known and convincing, and it just stands out a lot better in contrast against the cleaner setting. Costumes play a role here, too: the gross-out event is more disgusting when people are wearing normal clean clothes, than if one of them were dressed in overly filthy clothes. Regan spewing vomit in The Exorcist, for example, compared to a similar scene in the recent remake of Evil Dead.
In the 21st century, horror makers have encrusted their sets with gore and filth based on the belief that clean sets = dull sets. In reality, cleaner sets allow for a disturbing atmosphere to gradually develop, and for occasional gross-out moments to trigger disgust in the audience. Overly messy sets are just distracting, unconvincing, and therefore non-threatening. Perhaps that's the ultimate goal in this period of falling crime rates -- to make horror sets so unbelievable that we won't be in any danger of feeling unsettled.