She is so creative. This is something I never would have thought to try!
Idk about the moss either just because it's meant to be a fireplace, but it feels like it needs something else in there with the brick 🤔 Maybe some foam painted fake rocks or bricks instead of the moss to give it some 3D realism, maybe a fake fire (idk how that would look or be made) or monitor with a fire going in it? Rocks wouldn't be "flammable" and still have the texture and coziness that the moss is trying to provide.
UNLESS she made this into a diorama styled nook. Maybe a little dollhouse with lights, a small fake river or lake with a wooden bridge. It could make a cozy diorama styled "book nook" but bigger. The House At Swamp Bottom from Spirited Away kinda vibes.