General:
* Peaceful
* Tranquil
* Serene
* Calm
* Quiet
* Still
* Harmonious
* Gentle
* Soothing
* Relaxing
* Pleasant
Positive:
* Joyful
* Content
* Happy
* Hopeful
* Loving
* Kind
* Compassionate
* Tolerant
* Understanding
* Forgiving
* Respectful
Negative:
* Uneasy
* Restless
* Troubled
* Anxious
* Tense
* Hostile
* Aggressive
* Violent
* Unsettled
Specific:
* Silent
* Deep
* Inner
* Lasting
* Fragile
* Precious
* Unbroken
* Worldly
* Global
* Domestic
Figurative:
* Balm-like
* Edenic
* Heavenly
* Blissful
* Euphoric
The best adjective to use will depend on the specific context and what aspect of peace you want to emphasize.