what you see in the image is not a room, is just a basic editing of the textures of the game that anyone can do, in the case of the image I remember that are 2 different textures edited, to the wall was applied a layer with that texture and for the bed something similar, later I even got to edit the floor but it was more laborious because you have to add the shadows separately because it is not a flat color as the walls or the bed. .. has already been posted before but with IOTextureReplacer.dll you extract the textures with Alt+F11 and then put them inside BepInEx\Images so they appear in the game
btw you can enlarge all the textures of the game x2, x4, ... the limit is your video card, I did it with gigapixel