|The floor is lava|
In the campaign I play in, it is all homebrew content. In the world the GM has created, the available races for play are the standard set from the core rulebook, plus some extras like lizardmen and a homebrew race similar to elves. Anything more exotic than that is up to GM discretion, and typically comes after having a discussion with the player where the GM makes it very clear that if you choose one of those exotic races, you very well may be either the last of your kind, or from a entirely different continent. With that being the case, you will be constantly scrutinized because no one knows who or what you are. He will not handwave it to make it easier. Most times this pushes people back towards the more "common" races. But if you can make a convincing argument that you are capable of role playing this exotic race, he will allow it. I am currently playing a lizardman in a party of humans and dwarves, in a human-centric society. It's fun.