When I say something unique, I mean something that stands out about them. In Game of Thrones, what stands out about the Crannogmen is that they are small, northern people that live in swampy areas and are sneaky guerrilla fighters. What defines the Dornish, is that they live in deserts, are a very exotic people and culture, and are fiercely independent. The Ironborn are a people who live on nasty, wet islands and take everything they own from other people. So on and so forth. 

It was a suggestion more than anything.