¿Quizás palmeras en las playas y en las islas para darles más ambiente?
La verdad no sé que proponer, pero las ideas de Kefaku son muy buenas.

Here are a few ideas, you probably already had at least some of them yourself:

• Pirate: Custom mob, probably based on pillager, could have custom abilities/drops/weapons/armor/texture; captain, who is stronger; pirates could also carry/drop spyglass
  
• Ship: since there are shipwrecks in minecraft's oceans, having a regular ship structure similar to the shipwrecks would make sense; maybe you could also change the shipwrecks; pirates could live on these ships; loot similar to shipwrecks
• Treasure: custom weapons and armor/items that apply attribute modifiers or give special abilities; could be found in shipwrecks/ships/buried treasure or obtained through fishing (make sure not to make stuff to common)
• Costal Village: new village type; always near an ocean; docks/pier extending into the ocean; villagers could sell fish/boats (+ chest boats)/some more common treasure

Not typical pirate stuff, but this also came to my mind and might be cool:

• Nether Pirates: similar to pirates, but based on piglins; stuff they trade is different from regular piglins; ships on lava, instead of water
  
• End Pirates: similar to pirates, but with floating ships in the end; shipwrecks for end pirates could be slightly broken, but still be able to float through the void

I've thought about those last two for a while now and it seems pretty hard to implement, but it would definitely be cool if you managed to create buried treasure and treasure maps similar to those in the overworld for the nether/end variants.