The Jolly Roger - provided that they fly it - would be a legitimate inclusion in a Shipbucket drawing. It's their organizational insignia, and as you'll note, it's not even a Jolly Roger technically - it's not meant to be a sign of intentional lawbreaking.
I partially disagree: it does not exists "the" Jolly Roger but each pirat was having its own flag decorates with skull, skeleton,...
From this point of view the Sea Shepard flag becomes one of the last flying jolly roger.
And probably they had much more money than somali pirates, enough money, for ships, for flags, for web site, for press conferences,...