This post is provided for general informational purposes only and is not intended to be legal advice specific to you. This general information is not a substitute for the advice of an attorney in your jurisdiction. The attorney client relationship is not established by this post.
No, not necessary.
The above is general legal and business analysis. It is not "legal advice" but analysis, and different lawyers may analyse this matter differently, especially if there are additional facts not reflected in the question. I am not your attorney until retained by a written retainer agreement signed by both of us. I am only licensed in California. See also avvo.com terms and conditions item 9, incorporated as if it was reprinted here.
The legal issue here is that when you use someone's likeness or image this may be violating that person's right to privacy and publicity. These are state causes of action and each state has a different take on how they apply this protection. For example, some only protect celebrities or public figures, others protect anyone and still others will extend protection to dead people.
That said, even those states that protect dead people will only do so for a limited amount of time (generally no more than up to 10 years after death) and certainly historical figures like you noted would not be protected anymore.
You still need to make sure that you are not violating anyone's copyright interest however by using, for example, an image of some figure that is really a artistic work or graphic that is currently protected under copyright laws.
DISCLAIMER: this is not intended to be specific legal advice and should not be relied upon as such. No attorney-client relationship is formed with the law firm of Natoli-Lapin, LLC on the basis of this posting.
Frank Natoli's answer is correct -- the short version is no, the likenesses of these historical figures would not require licenses but you can get caught up by accidentally using copyrighted material (so make sure the quotes you are using come from the actual subject and not Civ V!)
I focus my practice on (video) gaming industry, casino gambling, and complex internet law issues, electronic free speech, entertainment law, copyright and trademark law, and computer fraud. I primarily represent game developers and founders of emergent internet technologies. The author is a Maryland attorney; however no answer given on Avvo is intended as legal advice or intended to create an attorney-client relationship.