Firstly that ship is very impressive - I like!! Though I can see where you are coming from with it looking slightly bland. The following are a couple of things you might consider:
- Skulls/Totems (ala the pirate ship in the substory from 'Watchmen')
- Banners/Crew colours
- Jolly Rogger
- Barrels/Crates/General stowage
Just some ideas that you might find interesting...