Yes, INTERIORS is a Scrabble word!

Letter values in Scrabble US: I 1, N 1, T 1, E 1, R 1, I 1, O 1, R 1, S 1.

Is it a valid word?

INTERIORS is a valid word in the official Scrabble dictionary (US), the UK Scrabble Dictionary and Words with Friends (ENABLE).

the region that is inside of something
the inner or enclosed surface of something
the United States federal department charged with conservation and the development of natural resources; created in 1849

Also: department of the interior, interior department.

Not playable in Scrabble US: DOI.