I started writing up some character background pieces, and started losing interest pretty quick. That's a good indicator that such efforts aren't going to keep the momentum going for me. With that in mind, I believe I'll make a few notes on some campaign/adventure ideas to further explore in the Isles of the Saharan Sea campaign.
The original Pellucidar series, by Edgar Rice Burroughs, provides plenty of fodder for adventuring in a Hollow World setting. These novels inspired the whole World Within concept, and I'd be a fool to disregard the tales of the aftermath of the collapse of the Mahars, and how the various cultures dealt with that. There are plenty of great opportunities for integrating elements of those story lines as adventures. In addition, the series is highly recommended simply to help create the mindset for playing in this kind of setting.
The classic adventure novel Treasure Island by Robert Louis Stevenson is perhaps the quintessential pirate story, and thus the quintessential pirate adventure. A young lad steals a logbook and a map that lead to a huge treasure buried on a distant island. They launch an expedition, only to find that a sailor seeks to mutiny against the Captain of the vessel and steal the treasure for themselves. The pirates follow the map, find the treasure has been excavated, and then are ambushed by the former leaders of the expedition, who had previously recovered the treasure. (Well, not exactly, but close enough for adventuring work.)
Now We Are Free!
Numerous Sword and Planet stories center around the use of slaves to propel ships across vast ships. The hero is invariable captured and becomes an oar slave early on in the story, but manages to break free, release his fellow slaves and stage a mutiny. The now-freed crew decides to become pirates under their savior, and travel the seas, stealing from pirates and the merchants of evil lands while freeing slaves from the oars as the opportunity presents itself. Obviously a piratical version of a "Rags to Riches" story, this kind of adventure arc would also be fun to run.
Sea Hag's Curse
Pirates are a superstitious lot, which gives us tales of curses galore to draw from. From those inspirations, we could easily draw an adventure surrounding the curse of a dying sea hag, and the efforts required to lift that curse.
Davy Jones' Locker
Davy Jones' Locker refers to the bottom of the sea, the final resting place for drowned sailors. However, Davy Jones has also been described in the 1700's as a demon "having saucer eyes, three rows of teeth, horns, a tail, and blue smoke coming from his nostrils", or it could be an evil ghost or spirit. This makes me think of an adventure or a small plot arc involving undead sailors attacking an underwater city, and the player-characters being called up by the mermen inhabitants to help clean up the mess their dead have created. Another adventure could center on the demon described as Davy Jones, or that could be worked into the first idea as the Big Evil Bad Guy leading the undead against the underwater city. Alternately, this could be an underwater lair that the PCs will have to explore magically to stop raids from undead walking up on the beaches from under the waves to attack.
Captain Ahab's obsession with an albino whale makes excellent fodder for an adventure focused on hunting leviathans, or at least a particular leviathan. Add in some supernatural elements, throw in a quest for an enchanted harpoon capable of slaying the beast, and you've got some good foundations to build on for a memorable adventure, I think.
The legendary ghost ship that could never make a port, doomed to sail the oceans forever, could also make for a great adventure. In the World Within, where it is always a noon day sun and night never exists, the concept of a weathered and tattered ship sailing amidst a cloud of foggy mist sounds interesting. Seeing it at a distance is easy enough on the open seas, thus it could be avoided. However, amidst a group of small, tightly packed islands, it would be easy to imagine such a vessel taking a ship by surprise. Adventures featuring a ghost ship might focus on retrieving a lost spirit or treasure trapped aboard the vessel itself. More ghost ships can be found on Wikipedia's List of Ghost Ships, which might provide even more inspiration.
While not a pirate story, the tale of King Kong starts off on a tropic island. It conjures to mind a tribe of native islanders that worship a colossal animal as a god, and the possibilities of being sacrificed to the beast as tribute. This kind of adventure story or site doesn't have to be about a giant ape; dinosaurs and other gargantuan beasts could easily take Kong's place in the tale. In fact, one of the old D&D adventures, Isle of Dread, could serve as a great resource for adventures, encounters and other fun elements to be included in an Isles of the Saharan Sea campaign.
Anyway, I'm sure there are more sources of inspiration out there for pirate-flavored adventures, in addition to whatever the players come up with as they move through the setting. I'll keep thinking on it, and see what I can come up with to supplement the above list of inspirations.
Avast There, Ye Scurvy Lads,