Hi! This sounds like it might be hypnagogic imagery, which occurs during the period between sleep and wakefulness, and is linked to the sleep deprivation you described (this article sums it up pretty well). Though the imagery experienced during this period is labelled a hallucination, people are often able to manipulate at least a bit of what they see, explaining why you were able to control what images you were seeing. Some people with aphantasia (including myself) have reported experiences of hypnagogic imagery, suggesting that it is likely linked to different parts of the brain than typical visual imagery! This old discussion post has a lot more information about this phenomenon (as well as some anecdotes of aphantasiacs experiencing it), as does this Reddit post and this article from the World of Lucid Dreaming.