Okay I though of a few examples of tribes as I went about my day here would be some examples.
The Tribe of Ish: Their skin is rather pale and they resemble an ancient Celtic tribe, with slight variations of course. This tribe wears no clothing and has Celtic tattoos cross their body to not only serve as decoration but some times even to tell a story of a certain battle they had been in or a marriage to another tribe member. There eyes are impossibly green and their hair color no matter blonde, black or red is just as vibrant. These plains dwellers are know as the children of the blood wheat by other tribes. Mainly because it is all they eat. Much like some of the species in our world they have found a certain plant that provides them with all their nutritional requirements. They use it in every dish if not the only ingredient. Not only is the plant nutritional but it also has a secondary effect serving as an aphrodisiac. Since it is there only food supply the tribe is constantly in a state of sexual desire. This of course shapes their customs. Sex is not seen as taboo or private but just another part of life. Nobody is monogamous and the tribe share each other with no question. Their traditions customs even greetings would be sexual.
This would be an example of one of the more human tribes. Of course there can be other tribes of more elaborate beings should anybody prefer. I would entertain any idea from orcs to elves to a special type of being.