I get to use my imagination in the backrooms, so here are some stuff I made
Room 651
Room 651 is the 652nd room in the backrooms, featuring a more lush, greenier variant of room 0. Dividing 7 by 651 gives you 93, and the 93 is obtained when you add 7, 18, 5, 5, 14, 13, 1, 26, and 5 together. This spells out “Greenmaze”. This is referencing Hollow Knight, as the music played here is a slowed down, distorted, creepier version of the greenpath ost.
Greenpath link: https://www.youtube.com/watch?v=ABXga9y0B3I
Room 3,260
Room 3,260 is the 3,261st room in the backrooms. It is a bigger brighter version of the 8th level of the backrooms. If you divide 3260 by 20, you get 163. The 163 is obtained when you add 20, 8, 5, 20, 18, 21, 5, 1, 2, 25, 19, and 19 together. This spells out “The true abyss”, which references Hollow Knight’s abyss. The music played down here is the abyss’ ost, but slowed down.
Abyss link: https://www.youtube.com/watch?v=4XxRUH8DOIQ
Room 2,140
Room 2,140 is the 2,141st room in the backrooms. It is a dark forest, much like room 651. Dividing 20 by 2140 gives you 107. This 107 is obtained when you add 20, 8, 5, 19, 21, 2, 3, 15 and 14 together. This gives you “the subcon”, which references a hat in time. The music that is played is subcon forest’s ost but creepier.
Subcon forest link: https://www.youtube.com/watch?v=aFsS_65zz4Y
Room 20,000,000
Room 20,000,000 is the 20,000,001st room in the backrooms. It is a giant room with a square layout while a turtle sings in persian (link here). This is a reference to the “Persian turtle” meme, as T in an A1Z26 Cypher is 20, and there are 6 extra 0’s, as the word “Turtle” has 6 letters in it.
Persian turtle singing link: https://www.youtube.com/watch?v=D4Jn6hW-T2I
Room -48
Room -48 is the -49th room in the backrooms. It is a tundra with a cabin (Much like Tirsiak’s starting room), but mirrored. It was chosen as -48, as she is the 4th unknown specimen and the - acts as a mirror.
Tirsiak’s theme: https://www.youtube.com/watch?v=_Go8viNVuAA
Room 30,008
Room 30,008 is the 30,009th room in the backrooms, featuring an Unlimited Ickea. It is a play on words, as the Ickea is spelled comically incorrect, as the real name is “Ikea”. This is also a reference to the 3,008th SCP, taking the form of said Ikea.
Room 292,439,477
Room 292,439,477 is the 292,439,478th room in the backrooms, taking the form of a metro. This is because the map is based on Phantom Forces’ metro map, as it’s the most iconic one of them all.
Room 444
Room 444 is the 445th room in the backrooms, taking the form of a claustrophobic trench system full of spiders. This place is darker than level 8. Dividing 4 by 444 gives you 111. By using A1Z26 Cypher, you get 4, 5, 5, 16, 5, 18, 14, 5, 19 and 20. Converting this gives you the term “Deepernest”, which is a reference to Hollow Knight’s Deepnest. The ost is Deepnest’s but it is somehow creepier. There are also 2 references to 2 games; a poster for Nyakuza Metro from “A Hat In Time”, and a poster of Embry, the main character you play as in the Indie game “It’s Not Me, It’s My Basement”
Deepnest ost: https://www.youtube.com/watch?v=0V9Uep3k1lo
Room 297.18
Room 297.18 is the 297.19th room in the backrooms. It features a Russian battlefield from the 1940's. The 297.18 is the product of the equation 7.62x39. This is the caliber of the AK-47. The ost here is a distorted version of Fort tundra's free time
FT's free time ost: https://www.youtube.com/watch?v=9YkeMm2k9rM&t=228s
Room 3105
Room 3105 is the 3106th room in the backrooms, taking the form of mutated sewers. Dividing 23 by 3105 will give you 135. Using A1Z26 cypher, you get 23, 1, 20, 5, 18, 23, 1, 25, and 9. Converting this gives you the word "Waterways". This, of course, references Hollow Knight's royal waterways. The music isn't like any other ones. The music is a more melancholic version of royal waterways' ost.
RW ost: https://www.youtube.com/watch?v=zkoTXeVinT4
Room 216.84
Room 216.84 is the 216.85th room in the backrooms, which takes form of an American military camp. This is because the number is the product of 5.56x39, which is the standard American military caliber. This is also backed up by the fact the ost played here is K.A.P.O.W Camp's Free time ost but it's reversed.
K.A.P.O.W Camp free time: https://www.youtube.com/watch?v=ZvCfx4sNeh0&t=144s
Room 7,000
Room 7,000 is the 7,001st room in the backrooms. this takes form of an abandoned prison. Said prison closely resembles the one in The Escapists, or Stalag Flucht. The ost here is stalag flucht's. This is also backed up by the fact that the original number was 70 (as Stalag Flucht is the 2nd prison in the escapists). Using A1Z26 Cypher, you get 6, 12, 21, 3, 8, and 20. Converting this gives you the word "Flucht".
Room 20,640
Room 20,640 is the 20,641st room in the backrooms. It is a calming room, as it features a large garage with cans of paint and a paintbrush. With this, you could paint. There is calming music playing in the background. This is because it leads the player into a false sense of security.
Room 10,660
Room 10,660 is the 10,661st room in the backrooms. This is a medieval castle. Inside this castle are axes (specifically Halberds or Battle Axes) and swords (specifically Excaliburs or long swords). There is also a grappling hook. This is required to get on top of the castle to progress to room 10,661. There are 2 references here. These are the Battle of Hastings (which happened on 1,066) and the DLC prison in the Escapists 2, Dungeons and Duct Tape (the grappling hook).
Room 292,439,476
Room 292,439,476 is the 292,439,476th "room" in the backrooms. This is because it isn't a room. You are on an train. The only objective is to escape. If the player succeeds they go to room 292,439,477 (the Phantom Forces one). If they don't they get sent back to room 0 (1/1,000,000 chance they'll be sent to room A). After completing the Nyakuza Metro-inspired area (room 292,439,475), they will be sent here. The OST is a more intense version of Cougar Creek's.
CCR OST: https://www.youtube.com/watch?v=LEmxfJwSP74
Room 292,439,478
Room 292,439,478 is the 292,439,479th "room" in the backrooms. This is another transport one, but this time, you are on a boat. You do NOT want to escape (if you're looking to progress), because doing so sends you to room 292,439,495 (the Nyakuza Metro-inspired area). The ost is a more "strict" sounding version of HMS Orca's
HMS OST: https://www.youtube.com/watch?v=RBieg_xm5FE
Room 292,439,479
Room 292,439,479 is the 292,439,480th room in the backrooms. This one is like room 20,640, as both are set up as a calming atmosphere. This one takes the form of the area in Hollow Knight, known as the "City of Tears". Despite this one having a calm soundtrack already, the ost is a more calming variant. The room's purpose (like 20,640) is to calm the person down to lure them into a false sense of security.
CIT ost: https://www.youtube.com/watch?v=1unm0LS10ao
Room 292,439,497
Room 292,439,497 is the 292,439,498th room in the backrooms. This takes place in the world-renowned prison known as "Alcatraz". This takes the prospective of one of the 3 escapees. You need to break out to get into room 292,439,498. The ost here is "Alcatraz", the free time ost for the one in TE1 (the escapists 1).
TE1 "Alcatraz": https://www.youtube.com/watch?v=SL1hlxwdWyk