Yes, the word peace is a common noun, a word for any peace any time, anywhere.
A proper noun is the name of a specific person, place, thing, or a title; for example:
- Peace Corps (volunteer organization)
- Town of Peace River, AB, Canada
- The New England Peace Pagoda, Leverett, MA or Japanese Peace Pagoda, Darjeeling, West Bengal, India
- "Peace Like A River", a novel by Leif Enger