The Donald Maass Literary Agency, which specializes in a fiction and represents the full spectrum novelists from romance to horror, literary to young adult, runs a feature called "What we're looking for this month."
Anything that sets a writer's mind working is a good thing, and anything that sets your mind exploring a new direction has the potential to be a very good thing. The Maass agency is taking a chance, with this column, of getting a lot of formula ideas written to do exactly what they say they don't want: "Our intention is not to suggest paint-by-numbers plotting or to limit the author's scope." But they probably get a lot of that, anyway.
Thinking about historical characters in a fresh way can get you to thinking about new conflicts, new settings, new ways of getting out of yourself and engaging the world.
Here are a couple of their suggestions:
J.P. Morgan – Intrigue and murder during J.P. Morgan’s single-handed rescue of the American banking system in 1907.
Ayn Rand – A New York detective investigates a murder following the Objectivist philosophy of Ayn Rand—and finds that the case leads to the philosopher-author herself and her circle of acolytes.
Read the rest; it's an interesting list. And bookmark their "What we're looking for" page.
The Ayn Rand suggestion is a good illustration of one of their other points: "The historical figures need not be a point-of-view characters; indeed, it may be better if they are not."
Caleb Carr has had considerable success setting an exciting murder mystery amid a tapestry of historical characters. His novels actually irritate me a little, because his characters seem to run into nobody but the most iconic figures of their time; I'd rather make the acquaintance of some fascinating but lesser-known figures. Still, who am I to argue with success?