So the list so far is as follows-
Goblins (Sand, Mountain, stone etc. )
Elves (Dark, white etc. )
Dwarves and gnomes - On the note of dwarves, I believe dwarves live underground, and are techinlogicaly advanced, while gnomes live above ground and are as average as humans yes?
Animal-Humans (Mermaids, centaurs, satyrs things of that sort)
Demons, but only if summoned. They are not natural entities.
Giants- (Like Hargrid minfigs a little taller is ok too, but nothing over, oh I'd say, the 10 ft range in relation to minifig size ) Also on the note of giants, I believe they should only inhabit remote mountains and other places, (islands, tundra etc. ) be slightly uneducated and slow, but not full trolls. They should live in like clans of 20 and in camps. Maybe we could add a couple camps to the official map.
My suggestions to the list-
Fairies (Good and Evil)
Trolls ( Live in caves snowy environments, are as tall as giants but not very civilized or smart. They're like giants' dumb cousins. )
Not really a race, but more of a class for all races, maybe like elders and monks who live exclusively in exile. Like an oracle of wise people.
All the others are just as good, but one question, what are sirens?
Sirens are mythological creatures from I believe Greek and Roman stories, most notably The Odyssey by Homer. They are similar to mermaids, some stories have them with fish tails and some don't, they are all women, and what they do is sing to sailors, or tell them of their future, leading them off their ships, so they can eat them. Google will probably explain better than I will