What I pictured when I read the word "Thin Air" was a person, struggling to breathe at high altitudes. More specifically I visualized a man traveling on a air plane, requiring oxygen from the air vent above them, and perhaps receiving an oxygen mask as the air level drops.
I am fairly good at visualizing images. I am a daydreamer with an active imagination that tends to run away with me.
To answer the second question, I don't think after seeing an an image once I have any exceptional ability to retain it in my memory over time. I have a good memory, but I am a much more verbal person, and while I am good at recalling names, or remembering the exact words that were said, and tone of voice, I am not as good with reconstructing faces or what someone was wearing.
I don't have very good eyesight. Though it is corrected to normal with contact lenses, I think my other senses like sound have developed to be the dominant ones that I rely on more than vision.