As of version 0.098, this game is playable again. More was added to the game as well, so the game starts out differently from what it used to. Below is a walkthrough on how to complete the game and get wallpaper #56.
Walkthrough
After watching a short scene, you will be in a dark room. The door behind you will be locked, so go down the stairs and the lights will turn on. There is a black figure in the room which will kill you if you get close to him. Go back up the stairs and you can now use the elevator, which is the blue doorway next to where you came in.
Go up and into the doorway with the blood splatter in front of it. Go all the way to the other side of the room where there is a gap in the chairs. If you try to go left books will fall and block your path, so go up and between the bookcases, then down and around the other bookcases, and pick up the item.
Go back out into the hallway the same way, then go down and straight right into the other doorway. There is a computer here where you can save your game. Note about saving: you will exit the game every time you save and you will automatically lose your save file if you start a new game, so be careful not to hit "start" when you start the game back up (saving your game at the computer in your room is a good idea incase you do). The blue doors in this room are locked, and in order to unlock them you will need to kick the blue stool over onto the blue tiles to the left.
Go through the doors and you will see some people walking left. There is a black figure which will get you if you try to follow them, so go through the doors straight up. The doors will lock behind you, so go interact with the NPC standing against the wall. He will start chasing you, so run to the door all the way to the left to escape him.
In this room there are four blue stools around and you will need to kick each one onto a different set of brown tiles. After you do that, leave the room and go into the door straight down. Pick up the key on the table and leave. You will see someone walk by, so follow them then go down back into the room with the computer. Leave this room and use the elevator to get back to the room you started in.
Go down the stairs. If you try to go straight down, the black figure will kill you so go left between all the shelves and go through the doorway on the right (the one on the left is an elevator which will take you back to the hallway). Go down the stairs then walk all the way to the left. Upwards is another black figure so go down and into the first doorway.
Grab the red item on the tables in this room. If you interact with the black thing in the bed, it will disappear and blood will appear outside of the locker. If you then interact with the locker, you will be killed. Leave this room and go into the next door downwards.
Interact with the computer with the red text to turn on the power. You can now save it at the computer on the far right. Leave the room. There is a black figure right outside and after laughing briefly, it will chase you. It will probably take several tries, but you will need to escape the figure and run straight upwards and into the door. There is a dog mask NPC waiting for you. You will then be caught and you will wake up in a room with a single bed.
Leave the room and you will be in the Art Room where the game used to start in. This part is done the same way as it used to be and you will get the wallpaper after completing it.
You first go into the left room, and notice the tile on the wall. Your basic goal in this room is to make all of the tiles look like the one on the wall. When you've done that, go up the the wall and press Z facing the tile. You will notice that the paintings that were once four halves have now come together to make two whole paintings.
Next, go into the right room and go into the very top right corner and press Z, which should open the door. (Pressing Z at the door won't work: You have to go to the right of the plant next to the door and face the door's side of the wall.) You will notice a big red piece of fabric on the wall and four small walls with paintings on them. Collect the paintings on all four walls until they are all on the fabric. Now go up to the black square and merge the half paintings together again.
In the lower-right corner of this room, there is a secret door right under the plant column. It leads to a seemingly empty, grayscale room, with a dresser, a stool, and a mirror. Interacting with the stool will show an empty dialog box, suggesting that there is some kind of ghost sitting in front of the mirror. If you bother it too much, it will kill you by grabbing you by your head.
After finishing the painting puzzle, go back into the main room, and you should now be able to go through the middle door.
After a cutscene where you see someone wearing a dog mask with grey hair and red school uniform is following you, you get transported to a corridor maze where you have to keep moving in order to continue (The map name translates roughly to "Different dimension corridor", meaning that by going through the door, the girl must have entered another dimension). If you come across a dead end or stop walking, then the person wearing the dog mask will possess/kill you, and you will have the option of trying this part again. The map for this area can be seen here .
After completing it by finding a door, you have to quickly run down two short flights of stairs, as the dog person is still chasing you. After escaping the dog person, the game will end and you will have the wallpaper.