Greetings!
In my Thandor Campaign, I have created many distinctive races of humanoids. Animal Hybrids, Reptilian Hybrids, Insect Hybrids, and more, in addition to Elves, Dwarves, Halflings, and Gnomes.
I also blend different Human races together, different ethnic groups, blending and creating distinctive and unique cultures.
Of course, historically, we have many examples. Siberians--a mix of North Asians, with Russians, Fiinns, Balts, and Norse. Evidently, Asian and European intermixing has been going on for thousands of years, going way back into prehistoric times.
Kazakhs--mixtures of Asian Steppe Nomads, Turks, and Europeans. Later on, of course, Mongols.
Hungarians--European stock of Slavs mixed with Asian Steppe Nomads. That is a pretty interesting story right there, of how the Kingdom of Hungary was revitalized by an official policy that mandated and encouraged blending with several Asian tribes that the Hungarian King invited into the Kingdom. Apparently, after years of fighting the Mongols, the native male population had of course suffered terribly. Then, along came some Asian Steppe tribes, trying to flee from the Mongols--and the Hungarian King said "Hey! We can help each other!"
Filipinos--Yes, look at the Phillipines. An interesting blend of white European Spaniards with Asian Island people. 500 years later, we have a distinct and wonderful Filipino culture and people.
Mexicans--Mexico, of course, blending Euopean Spaniards with Native Indian people. Now, 500 years later, Mexico may as well be their own race, forming a distinctive culture that blends their Spanish and Indian roots. More recently, with extra Gringo American spice.
There are many examples. I think it is fascinating how there can be two--or sometimes more!--cultural or racial influences, that combine, and create something new and distinct, different from the original foundations.
These kind of inspirations from history can contribute greatly to the fabric of a great game campaign. However, embracing such may unwittingly bring in more family and cultural details--especially influencing a character's background. I know some people get all squicky about having dreaded backgrounds that are fucking detailed, but to my mind, the depth, the details, and the fun make it worthwhile for a good campaign.
Fantasy campaigns of course not only have human groups, but also humanoid and crazy animal races. The variety is endless, and the different cultures that can be created and developed can be very interesting.
I highly recommend embracing such ideas for a great campaign!
Semper Fidelis,
SHARK