For my Pleistocene Sword & Sorcery setting, which has been perpetually on the backburner as I've developed my other main setting, here's some examples of the correspondences I'd like to use. Calques, if you will, where one culture is migrated from the real world setting into the fantasy setting with an almost one-to-one correspondence. Certainly, unless claimed otherwise, you can assume that something that you know about, say, the Vikings will apply to the Vendel, my fantasy version of them. Here's the list:
Vikings : Vendel
Saxons : Hæstingas, "Haestings"
Celts (Scottish/Irish) : Gaidhel
Byzantines : Komnenians
Slavs : Kayazy
Turks : Vatheks
Algonquins : Mawrocs
Iroquois : Manahatts
Chinese : Fusangians
Plains Indians : Tatankens, Nakota, Nuumu Komantsi
Cliff dwellers : Kayenta
Aztec/Maya/Toltec (combined for ease of use) : Tlanoc
Mound builders : Cahokia
I might need to come up with some North African, Sahelian, and Middle-eastern calques as well, but let's not get ahead of ourselves. And, of course, I've got Muans, Lemurians and Atlanteans to deal with as well. That's certainly more than enough to get up and running, covering almost all of Europe and North America. That's more than enough setting for the time being.