So really it depends on the culture you want to promote and what is necessary to keep your employees happy and content. Measures can be put in place based on what the competition is doing and also on what is required to help/encourage the employees perform better.
Found these few articles which may be of use:
The perks of being a startup staffer - Ranjani Ayyar
What unique benefits do start ups offer their new employees? - Quora
13 priceless benefits your startup can offer potential employees - Mashable
3 Perks Every Startup Should Be Offering Employees - Fortune