Need help with photorealism

Hey Liquid, good attempt at modelling, but the surfaces look too clean. You should try using more bump, specularity and displacement maps. Also some overlays for imperfections. The grain of the blocks also seems a little too large. The bed material could use a fresnel fac if it doesn’t have one. And, take this with a grain of salt, but when in doubt use ambient occlusion. It helps simulate the darkening effect at the edges of overlapping objects which is found in the real world.

In that position of the camera I could even imagine you standing there taking the picture. Do not do that, you look for shots a little more parallel to the floor, as if you were squatting.
To best learn I think you should look for similar images on google (bedroom windows), and then try to emulate what you like.
Your materials and geometries are perfect (the opposite of what is needed in photorealism). You should not have so clean materials and very sharp edges, you look for more variations and imperfections. In the window glass you need better reflexes and not so clean around the edges. The atmosphere there also looks very clean.
You look on how to achieve realistic materials in blender, there are good tutorials out there. In Youtube: blender realistic, blender pbr.
And you also need compositing, colors corrections, some sort of Bloom effect and achieve dense atmosphere.

In addition to what YAFU said, something crucial to achieve photorealism are details. A real looking picture needs to show all these details we often forget in the idea we have in our mind.
For example, when you think about a wall, the first image that comes to your mind is the planar surface. Cool, it is 95% of the wall. But what about the baseboard? What about all the sockets and switches?
Look for reference along the web and here in this forum, there are many examples of this.
Good luck, and keep on working!