Merry Christmas - С Рождеством!

peace on Earth - Мира на земле!

Wishing you a beautiful Holiday season - I think it would be better to diverge from the translation word for word and to put it like: С наступающими Вас праздниками!!

С наступающим! - It's the most frequent phrase in New Year Eve. You are likely to hear it everywhere: in shops...everywhere