According to Official Guinness Records,
The largest human playing card consisted of 600 participants at an event organized by the Turning Stone Resort and Casino (USA) in Verona, New York, USA on 13 July 2013.
Participants wore either a white or red rain poncho and were directed into position to form a human version of the ace of diamonds playing card. The record attempt was made to help Turning Stone Resort and Casino celebrate its 20th anniversary.
For a complete list of 2013 records, please visit 2013 Guinness Records in United States.