Two books containing two-page spreads for over a hundred figures from history, from Alexander the Great to HP Lovecraft, Cleopatra to Sid Vicious, with suggestions for fantasy variants and, naturally, lots of ideas for time travel stories about them. The kind of books that Doctor Who GMs can dive into. It would be easy to pick one up, open it at random and run an adventure about...
Gráinne Ní Mháille, aka Grace O'Malley, Ireland's Pirate Queen. Okay, that's almost too easy. The obvious historical hinge point would be when she met Elizabeth the First and bargained for a pardon for herself and her family in exchange for sailing against the Spanish. All kinds of sinister powers would want to disrupt that meeting and provide a back door to attack Elizabethan England, and the PCs get to team up with a Pirate Queen to stop it in case you missed that bit.
Okay, let's try again.
Erwin Rommel, the Desert Fox, about the only leading German officer to get much good press in World War II. Pivotal to the war in Africa, and involved in a plot to oust Hitler and try him for his crimes. Again, it's not going to be difficult to mix him up with time travelling adventurers.
Catherine de' Medici, Italian noble, Queen of France, patron of the arts and generally terrifying. Probably not going to receive the kindest portrait in a Celebrity Historical.