Hi,
You may form Annual Day celebration planning committee consist of HR and one member from each department. Give free hands to the committee as to how to plan and execute the events. The Committee may call for interested employees to participate in the event to exhibit their personal talents like dance, mimicry, singing etc.
Added to the above you can suggest committee members to plan for some fun games with prizes.
During Annual Day celebrations you may recognize employees for
Best performance
Being punctual to office all days
award for less leave availed
employees who had completed 5 /10/15/20 years ( years as per your choice )
Conclude the celebrations with Dinner. Thank all the employees for the support extended.