For the full release I thought I'd go out of my way and give some criticism on your map to help you improve as a map creator. This will specifically be towards backrooms maps, and dealing with them where it would make the map more enjoyable for the player. Lets start.

1. Red lights: The iconic red lights that "Level !" is meant to be contain, fading off and back on is clearly not there, this on its own is a big thing due to the nature of this level. You need to make it so the player can't see very well what they are running into seeing how obstacles need to be present, making it much more difficult jumping over what you cannot see once the red lights reach the darkest point of fading, only to come back on and surprise the daylights out of you. That and they need to be present at even intervals along the hallway, along with an audible emergency alarm noise. This as a result will make the map much less easy and will actually feel like a challenge, like it should. It's a 10 km long hallway.

2. Doors that lead to nowhere: It is true that this level's door are all locked except for the one at the end of the hall, but that doesn't excuse the fact that in this preview the rooms and structure of where the doors are placed seem like they lead to nowhere. It gives the player no reason to try and check a door which leads to a room appearing to be smaller than a broom closet. Structure your map to where it seems that the doors will lead to somewhere, not just for vanity, but for false hope for the player. I noticed once you spawn the first left corner you take leads to a door which leads to nowhere, if you circle around you can see another door from the other side which is also locked, with the space in between them seeming like it wouldn't hold anything. On the note of doors, this is a personal dislike, but the door frames seem too bold, and don't give off the feeling that we as a player are in a hospital like environment.

3. Monsters/NPC's [Entities]: If you plan on adding entities to chase the player make sure you add them far back where the player can see them while also having a running start advantage, although having the Entities hold a speed advantage over the player, eventually reaching them if they prove to not be fast enough in traversing the level. If you struggle with getting a proper NPC, look at the workshop for mods. There is no shame in having mod requirements for your map, if anything there are even NPC mods for backrooms creatures that can pursue the player. Adding the fast zombie and changing its color is not gonna be as scary as seeing a plethora of faster than the player type monsters which pose a more realistic threat.

4. Obstacles: For this its pretty simple, just use mainly things you would find in hospitals and don't make them look repetitive, have each obstacle have its own challenge the player must face. This is where most explorers die, so difficulties come naturally with this level.

[FOR THE SOURCES USED IN THIS SUGGESTION I'VE USED THE BACKROOMS WIKI]