What historical settings? This'll be fun :-D
I'm currently using DFRPG to power a Steampunk variant of England in 1867.
The Wild West would be fun; anyone who's enjoyed Deadlands would have a blast here.
The Dark Ages of Europe could be a blast as well. The 12th-13th Centuries in particular would be interested with the beginning of what we know as the Inquisition, while the 15th would be fun due to the War of the Roses (as previously mentioned).
If you are going with even earlier, then we can get the classic "advisor" to the King vibe going. . .and possibly even using Wizards as siege engines.
There's also something about the conquest of Alexander the Great that would be fun, as well as just about anything in the Roman Empire (a friend of mine has been toying with the idea of running an RPG in that era; I'm going to nudge her with the DFRPG).
Honestly, if we were to limit to a location, I'd use Italy and pick somewhere between The Italian Wars through the end of the Renaissance.
Pirates would be neat. Dresden Files: Pirates would be like the Rpg 7th Sea, but you know, good.
Speaking of this, I've actually been in talks with some guys from my old gaming group as to how to properly emulate the magic and swordsman schools of 7th Sea for a potential conversion. The closest we tested was using PDQ, but didn't think it fit. . .
If you have any thoughts/want to soundboard, feel free to send me a message.