I'd make 72 images of life as we know it - to communicate, as best as I could, to a future generation or visitors from some other cosmic place, what life and the human condition was like at the time.
Oh wait, that's my next self-assignment!
Actually, I've done it once before 45 years ago, unintentionally, without having thought about it, but I wasn't limited to 72 images. I shot an immense volume - over 10 thousand B&W frames in my teens alone, in my home town. Many decades later I shared nearly a thousand of the best of those images with many hundreds of people both of and not of that era. Had I known then what I know now, I would have still have shot much of what I did, but would shoot even more variety with a visionary intent to make the most iconic images or normal life, people, places, and things that are truly representative of the era to be enjoyed long after I'm gone - aware of the deep and profound impact such images can have on so many lives.
Michael Firstlight