Riot, how much of Runeterra is 'unexplored' for us readers?

Runeterra is big. We know of only three continents and already have a shitload of content in each of them. Whether it be races, nations, languages, cultures you name it. However, if we were to write any stories of our own taking place in this world...how much can we 'make-up.'

For instance, other fantasy races. Goblins are a common trope with fantasy writing, but League doesn't really have a 'goblin'-esque flavor to it. The closest we have are Trundle's frost trolls, and 'Rise of Icathia' hints at a large population of other, smaller non-human races throughout Runeterra, especially near Icathia (as seen by Saijax/Jax, who is confirmed not to be corrupter by the Void, but rather that he's simply not a human by a Rioter iirc). Is it possible for new, smaller populations of intelligent races roaming around the world? Not even just Vastaya, who are already a very interesting and thematic group of races to work off of, but just in general?