Plywood finish for interior walls. There are many grades of it. Shuttering ply is cheap yet has a beautiful texture. Also requires a fire retardant treatment - roughly the same cost again on top, however still far cheaper than traditional wall finishes.
Vattenfall Arenastaden interior by Tengbom. On the ground floor of the building's atrium there is a common cafe and 'living rooms' on either side of the stairs, designed as bleachers with cushions and (Indoor Step Stairs)