According to Official Guinness Records,
The largest human image of an arrowhead numbers 323 participants, achieved by the City of Gatlinburg and Great Smoky Mountain National Park (both USA), in Gatlinburg, Tennessee, USA, on 10 August 2016. The attempt took place at Ripley's Aquarium of the Smokies. The image formed was a representation of the National Park Service logo, in honor of the 100th anniversary of the founding of the park service.
For a complete list of 2016 records, please visit 2016 Guinness Records in United States.