Humans think, what varies is the quality of the thinking.

Your most relevant questions was "Is there a break in thinking when no sensory input occurs?". My subjective experience is, absolutely not. I think better without sensory input. If my experience is generally applicable, then it establishes that thought exists independent of sensory input.

Creativity is and may remain mysterious, because by definition it's the generation of ideas without precedent. An idea is merely derivative if it has precedent. In some domains I might be accounted to possess some creativity, and my subjective experience of it is that it just happens. Stuff pops into my head, and if my conscious faculties don't filter it out as random noise, then I'll consciously act on the idea and develop it with more logical faculties. But a creative idea seems to pop into existence out of the vacuum like zero point energy.

There are conventional explanations for the phenomenon, like Freud's menagerie of agents jockeying for dominance beneath the surface of consciousness. Those ideas go pretty far at explaining consciousness, but not completely. Maybe it's because ideas like Freud's and Jung's were developed when Newtonian mechanics still held sway over the popular understanding of physics, so that thinkers in other fields tended to think of mechanistic explanations. A more modern point of view, that blends quantum phenomenon and chaos theory and the theories of emergent phenomena, actually allows for "it just happens" as an explanation as valid as particles popping into existence in the vacuum.

There are people like Ray Kurzweil going on about the "coming Singularity", and using language borrowed from physics to evoke an image of an event horizon in the near future, beyond which, by definition, we can't see (despite the willingness of futurists and sci-fi novelists to speculate anyway). One of the more esoteric threads is that brains and consciousness are quantum phenomena which emerge from and interact with the physical universe; one interpretation of "the Singularity" is that we'll acquire godlike powers over the physical universe. Given that consciousness and the universe may be inextricably related, the new answer to the question "if a tree falls in the forest with no one to hear, does it make a sound?" is no, not really, although in another branch of the multiverse the answer is yeah, sure, why not.

In Dan Simmons' Olympos, sequel to Ilium, the author explains the ability to travel to universes populated by characters out of human fiction as the result of a few singularly powerful imaginations, like Shakespeare, able to punch through the "brane" to universes which just happened to contain those characters. In other words, in a multiverse with 10^500 possible universes, somewhere you'll find one actually populated by Greek gods, and because it resembles something imagined by a human with a powerful mind, it's easier to get to those universes than those containing things no human has ever imagined.

I like it. It may be fanciful BS, but it's cool BS.