I found 2 boys, maybe brothers sharing a room in s9e1. Beds are horizontally aligned. The other boy in the left bed is darkhaired.
Pic 2 showing a better view of the attic with Laura and Mary sharing one bed wearing night caps (s1e15). Their little sister sleeps elsewhere, obviously downstairs.
Pic 3 showing an interesting Western-like green metal bed in the 2nd post-series movie Little House: Bless All the Dear Children (1984) (set around 10 years later, probably in the 1880s or 1890s).
Main entry, previously rating 5 at