You can do following employee Engagement activities in your office.
1) Birthday Celebration
2) New Joiner's welcome party.
3) Small Games on Team Building, self improvement, motivation etc.
4) Celebration for "Employee of the Month or Quarter or Year"
5) Award & Recognition party for Best Target Achiever.
& many more activities which may suit your Business domain, Operational Possibilities & HR Budget allocated to HRD.
This will surely give boost to employee's for contributing more in mutual growth.
13th January 2015 From India, Ahmedabad