Much of the imagery in part 1, chapter 1, helps to establish the ominous tone of the story and the threatening setting Winston Smith inhabits. From the opening sentence, both are fairly bleak:
It was a bright cold day in April, and the clocks were striking thirteen. Winston Smith, his chin nuzzled into his breast in an effort to escape the vile wind, slipped quickly through the glass doors of Victory Mansions, though not quickly enough to prevent a swirl of gritty dust from entering along with him.
The bright day is contrasted by the reality of the cold. Winston is trying to "escape" a "vile" wind and the clocks strike the ominous number thirteen (also heightening the alien-but-familiar nature of the story—as a normal analogue clock only has twelve hours). The imagery here allows the reader to immediately be swept into Winston's cold, unwelcoming world that is not too unlike their own.
Later in this same chapter, the reader is able to ascertain the total control of Winston's government from a description of his home:
By sitting in the alcove, and keeping well back, Winston was able to remain outside the range of the telescreen, so far as sight went. He could be heard, of course, but so long as he stayed in his present position he could not be seen.
This imagery allows the reader to conceptualize the far-reaching influence of the oppressive state into the private lives of citizens—monitoring their daily actions through the telescreen.
In part 2, chapter 2, Winston has been captured, and the imagery once again returns to show the now more threatening setting he finds himself in:
He was lying on something that felt like a camp bed, except that it was higher off the ground and that he was fixed down in some way so that he could not move.
Winston suffers more beatings than he can count, and the imagery is descriptive of his suffering as well as the moments in between them:
He remembered a surly barber arriving to scrape his chin and crop his hair, and businesslike, unsympathetic men in white coats feeling his pulse, tapping his reflexes, turning up his eyelids, running harsh fingers over him in search of broken bones, and shooting needles into his arm to make him sleep.
Even the conversations are vivid in imagery:
"You are afraid," said O'Brien, watching his face, "that in another moment something is going to break. Your especial fear is that it will be our backbone. You have a vivid mental picture of the vertebrae snapping apart and the spinal fluid dripping out of them. That is what you are thinking, is it not, Winston?"
The imagery is menacing in both sections of text—and throughout the book, for that matter. Orwell crafts language around the experiences of Winston Smith that use various sensory assaults to shock the reader to contemplate the idea of governments that gain to much influence and exert too much control over their populations.