The ones that come to mind are Priestmangoode & DesignQ.
There are others but not a lot that focus on whole cabin. More like seat design, galley design, lavatories, etc. More component specific.
JPA, Tangerine, Altitude Aerospace, Zodiac Aerospace are others.
It’s usually a collaboration/coordination between aircraft manufacturer, airline, design studio and the interior component manufacturer.
IDEO and BMWDesignworks also have done aircraft interiors. Many years ago, Eclipse aviation once hired IDEO to design the interior, Designworks to design the T&F and Zodiac Aerospace to manufacture the components. Zodiac recently created ZEO, their in-house design department, to potentially design & manufacture.