(Also assuming a time machine, obviously)
In the realm of:
World History/Politics - Gandhi
US History/Politics - Teddy Roosevelt
Biblical - St. John the Apostle
Military - Robert E. Lee
Letters - Mark Twain
Sports - Roberto Clemente
Movies - Frank Sinatra
Music - Jimi Hendrix (lol on your Keith Richards RIP)
Confucius, Homer, Ovid, Helen of Troy, Sappho, Catallus, The Medicis, Bertrand de Born, Walther von der Vogelweide, Chaucer, Attila the Hun, Widukind, Louis the XIV, Thomas Payne, Beethoven, Walt Whitman, Thomas Mann, Joseph Goebbels, Hassan i Sabbah, Melville, Sitting Bull, Rimbaud, Yeats, Man Ray, Ezra Pound, Gertrude Stein, Rauschenberg, Joseph Beuys (sp?), Picasso, Kandinsky, Faye Dunaway, Frida Kahlo, Jack Nicholson, Bob Dylan...
really any great old face, many nude, placed dwarved in an empty landscape.
Alexander the Great, Cleopatra, whoever made the Sphinx, Shaka Zulu, Rasputin, Chief Joseph, Abraham Lincoln, Geronimo, George Washington Carver, Harriet Tubman, Confucius, Harriet Beecher Stowe, Frederick Douglas, Bette Davis, Moses, Abraham, and the person archeologists named 'Lucy', her bones are some of the oldest ever found in Africa..
Oh, Keith Richards is dead... he just don't know it yet.
Someone should give the guy a break and tell him....
They can't afford to -- he's still making them too many millions.
I guess I'd like to meet/photograph the people I'm named for, Paul Robeson and David "Mickey" Marcus. Isaac Asimov, Isaac Newton, Marie Curie, Mozart, Socrates, Michaelangelo, DaVinci, the Montgolfier brothers (get the first aerial photos), Geronimo, Ambrose Bierce (who may not be dead).
My Grandpa and Grandma Smith. They were my best friends growing up but never had an official portrait done, heck there are very few shots of them together at all. ;(