While embarking on a new type of writing, creating alternate world fantasy, I rebelled against copying what I already knew. Instead I insisted on creating my own species and giving them my own names. However creative I attempted to be, they still resembled fantastic human-like creatures in classical myths. The cavelings dwelt in caves, raised fungus, farmed blind water creatures, and mined precious substances from the ground. When they wandered outside they stuck to the level ground and feared climbing trees or foot hills. That sounds a bit like dwarves, but the other species treat them more like trolls, and physically they don’t look like either.
How was I to make these cavelings original? I had to create a main character that struggled to overcome his fear of heights and his ground loving attitude to gain a reputation among the treelings (who live in interconnected tree houses) when they must battle some renegade skylings (who have come down from the mountains where they live).
If I modified common species, readers would carry over their prior knowledge of species, such as dwarves and elves. That makes it easier to get directly into the plot. But, the characters may either echo others that are very common or conflict with the readers ideas of what these species should be. When I create my own, I call the shots.
If you look at early Star Trek episodes the alien races were based on different human ethnicities: Klingons were vaguely Mongolian, Romulans were supposed to be a meld of Asians. The Vulcans were part European and part elf. To design an ethnic group and not mimic one that currently exists, you have to choose features that simply don’t exist in humans. However even this may not work. People may connect them with an ethnicity. In the movie Avatar, the indigenous race was noted by many people to be blue native Americans with tails.
People remember by connecting new things to ones they currently know. So, whatever behaviors and values that you assign to your invented ethnicity will be connected with real groups that show similar ones. The depth of individual character development is the key to making invented species memorable ones – just like it is when writing about humans.