I've seen a lot about CHiM which if I'm not mistaken is a theory that everything in TES lore is inside the dream of a great unconscious being. Well, what is this being living in? What surrounds it? Nothing? Or some other world? Does it even have a body, or is it just a body-less 'ghost'?

These are the questions that haunt me...

Also, I've searched 'CHiM' in the Imperial Library and I don't think I found anything. A link or two to something substantial on the topic would be greatly appreciated!

The Devs. Or the Game. Or the Master Copy of the Elder Scrolls timeline, if such a thing exists. The Imperial Library itself. The UESP Wiki. The Fans of the Series. Every Modder out there.

One explanation I've heard of CHIM (in fact, the first,) basically boils down to the idea that everyone who has acheived some manner of CHIM realizes that they're a fictional character in a fictional world, and decided to roll with it.

So, in answer to your question, the current CHIM creature would be...

Todd Howard.

Could be us, the developers, or even some guy in a coma siting in a hospital having a dream.

Dude... That's so deep I can't even see you anymore...

So... how does one achieve CHIM?

Not an expert, but to clear up some terms:

CHIM (all caps - try the TIL search again this way) is the successful realisation that one exists within the dream of a greater entity. Some people choose to interpret this as knowing you are a video game character, others do not. A handful of characters have achieved CHIM (Vivec, Tiber Septim, perhaps the Nerevarine). That's a simplistic explanation of it anyway, and as much as I'm willing to attempt (since if I go deeper I'm liable to mess it up).

The "CHIM creature" you refer to is the Godhead, the entity that dreams the dream. As far as I am aware, nothing is really known about him.

CHIM is a state, or a power, achieved by someone who realizes that their individuality is just an illusion, as they are just a figure in a dream. If this someone then has enough willpower to say "Screw you, dream, I DO exist!" then they can hijack the dream and manipulate it as if they were lucid dreamers. If they don't have that willpower, they just disappear.

CHIM is basically realizing you are part of a dream, the next step is waking up and starting a dream of your own and its called Amaranth. There is only 1 being that has achieved the Amaranth and it is the godhead that dreams the universe. That being's identity is unknown however.

CHIM translates to "royalty" in the elder tongue I believe.

Works just like a Lucid dream, almost.

The question also arises as to whether this godhead is really an entity or if it's more like the universe's natural laws of physics only more bendy than our own.