By the look of the posted screenshots/videos and user comments, the hidden people are refered to as the Huldufólk, creatures from icelandic folklore.
Being from Norway, I agree that they could be based on the Huldufólk, but looking at the pictures posted, I would say they are a combination of icelandic and scandinavian folklore. Iceland was a part of Norway until 600 years ago, so no big wonder why they should have common folklore.
In scandinavian folklore, we call the creature a "Nisse"(Norway & Denmark) or "Tomte" (Sweden).
They are small creatures, always hiding from humans, and often living on lofts in farms/houses, or more rarely in the forest. They like to live undisturbed, and can cause damage if not respected by humans.
In the Grickle-video "Hidden people", the scenario is a bit scary. Nisser is not seen as the most scary creatures in nordic folklore, but we have some other creepy ones:
He is a underworld creature, lives in ponds/lakes and tries to drown people or animals by attracting them with spell-music, or by luring them in other ways. It is said that you can hear his terrifying and tearful screams right before suicides or deaths.
Pregnant or young women, and unbaptized infants are prefered victims.
They are evil, ugly, strong human-like creatures. They appear after sunset, and in the night they kill and plunder. Some trolls steal human babies from their beds, and sometimes exchange them with their own ugly offsprings.
There are several other creatures in nordic folklore, you can watch a video of some here:
I actually hope the Pilot game is as creepy as the "Hidden People"-video, and I think it would be an interesting step for Telltale.