Updated: Aug 4, 2022
Most campaigns, whether fantasy, sci-fi or anything in between tends to have humans as their main race. This is understandable, there are few of us, even in the gaming world, who could be considered anything other than human. It is an experience that we know. But why not really mix things up? Why not have humans as a minority race, perhaps in a world where they are subservient to the dominant Orcs or a fledgling Empire on the edge of a multi-million years old, billions of light-years wide, super-advanced civilization. (If you like the sound of that, go and read Iain M Banks Culture novels.)
In fact, if running a fantasy campaign, why adhere to the stereotypical races at all, if you are building your own world why not populate it with new and unique creatures rather than the stuff of, largely, European mythology? Maybe that is a step too far, but there is nothing to stop you from introducing your own races, unique to your own world.
Next, you need to spend a bit of time thinking about your map. I have played in some game worlds where logic is in short supply and you move from kingdom to country that seem to have no business being neighbors. Your world, as fantastic and far-flung as it may be should still have an internal logic and just as in the real world, neighboring areas will affect each other culturally, They will trade, undertake diplomacy, and adopt each other's styles and trends and grow to mimic each other in many ways.
One of the best ways to think about this is, particularly if you are designing a fantasy landscape, to get a map of our world and then loosely draw your new world upon it. Then use some of what you know about the cultures of the real world to act as the starting point for designing the new world. Use the climate and clothing, look at who those regions traded with to create a mash-up culture, look at their neighbors and needs and slowly a logical new nation will grow.
The cultures of your space worlds can be a lot more random once you get away from the civilized core and are probably going to e more lawless and random anyway, driven by the resources that the economy is based on and perhaps even how close to a space lane or galactic neighbor that planet might be.
Interesting flavors might be to imagine alternate futures for our own earth and then apply them. What would the world look like if the Roman Empire had never fallen and had possessed space travel? What if the Aztecs had become an industrial power? What if the ice caps had melted and the population had to live on vast floating islands?
And, having briefly fleshed out your slowly blossoming world, spare a thought to its history. Empires rise and fall, cities are ruled by ever-changing dynasties and the power and influence of religions ebbs and flows. Perhaps sketch out a rough historical timeline. This will help you to understand your world as you see it today by understanding the past that it grew out of. It will explain how those ruined temples, ancient underground lairs and dungeons got there. And again, as you create new storylines, you can link them to events of the past, which again creates not only logic and consistency but can also be used as a source of secret information that your players might need to collect and unlock.
Don't get stuck in the ideas of the past. These are your worlds and you are free to create anything you like. The world, as they say, is your oyster. (Now there's an idea...is the World Oyster a vast space creature so big that you can raise a city on it or is it ancient mythology about how the world came to be born? It's up to you. It's always up to you.)
Have you ever homebrewed your own race for your campaign? Let me know in the comment below!