I'm not sure how common or rare this is, but the visual images I recall are stunningly lacking in detail. For example, in the case of people, even with someone I know very well, it is rare for me to be able to report so much as their hair color on the basis of the mental image I call up when I try to think of them. I don't seem to have any unusual difficulty recognizing people, or any tendency to confuse my various mental images with one another, and the mental images don't seem incomplete until I start thinking about questions like how to describe them. I'm sure I would be completely useless to a police sketch artist if I were ever a witness to a crime.