A few more additions to add to Bester Bageler's list:
Sonic detonators
To maintain morale, it is best to reduce the impact of a heated argument on the rest of the crew, particularly in the immediate area. A SD system can dampen raised voices to near-silence to significantly reduce the negative social effect on the crew, and to call in security or senior personnel to deal with the uprising.
Environment psychological replenishment chamber
Even nice, fancy, luxurious ships such as the USS Enterprise suffer from gradual morale loss; an environment chamber with the appealing ambiance of tropical rain forests with heavy rainfall and breezes makes an excellent replenishment for psychological wellbeing. An actual environment box for this is recommended, but a holoprojection chamber/holodeck will suffice.
Entertainment center
A functioning entertainment district, including board games, friendly competition, and performance greatly subtracts monotony.
Ambiance emitters
Depending on the mode of propulsion and the modes of other systems around the ship, the ship and/or its engines may or may not produce noise; some may hum, others a distant, low pitched rumble/thunder/roar, but some may be completely silent. If the ship or any habitable part of it is totally silent in its operation, it is best to lull the corridors with some pleasant form of ambient sound while there is no emergency/alarm. It is a tested and proven fact that total silence is an actual psychological danger; lack of sensory input causes the brain to generate its own, inducing hallucinations, which can eat away at morale and heighten superstition, which can and has lead as far as Self Delete and murder in long-term flights.
Hope this helps.