The majority of ships designed their own flags to distinguish themselves from other ships. Except for Sam Bellamy. He used the famous black flag known as the "Jolly Roger". It was a symbol known to all those on the high seas, the ominous symbol of imminent attack.
The term "Jolly Roger" encompasses any type of pirate flag. It is believed the term derived from the French, "jolie rouge," or "pretty red". During that time period red flags fluttered above many Buccaneers galleys.
Blackbeards flag featured a skeleton and a bleeding heart but the most famous flag to hail from that period is that of the skull and crossbones, representing an unforeseeable death.