I have just recently finished the game and found it to be a nice little find with a large tale
I grew up on old games that rarely ever used voice-overs, and when they did they were usually very shoddy. Reading has its own charm. It converses with the player's imagination, allowing him to actively in the game in a way that voiceovers would undermine. But that is for another topic.
As the Subject Title suggests, I was wondering if you have ever considered other avenues for Ghost of a Tale. A sequel would be great, and considering the favorable response to the game (I think), you may even be able to enlarge your team a little. But in the meantime offshoots could be an option to help ease the costs for future endeavors and enkindle more interest in it.
For such a small game you have conjured up such a large world. I found the use of "footnotes", songs, and books a clever way to relay the world without ever stepping foot off the island. What has been conveyed in those systems not even a couple or more sequels could fully exhaust, save perhaps if you changed the nature and the scope of your game. But considering that the plot was text driven, it would not be out of place to consider releasing stories about the world, its events, its people or history, through the use of short stories or by making a novel or two. In this way, even if a sequel did not manifest itself, the story could continue.
Should you desire to reserve Tilo's story for the game alone, a story chronicling the mission of other four would be still open. Sort of like Lord of the Rings, save we focus on the larger party's exploits rather than Frodo and Sam's- whose quest ended up being the more important one. Thus while the sequel game could continue to explore and expand on the ancient lore, reveal more about that devious Green Flame, and continue with Tilo's story, a novel would allow the reader to step onto the mainland and interact with the peoples and culture's of it. Might be interesting to see how an Orphaned Rat Prince raised by mice, a Rat Pirate who pretended to be a blacksmith, and two ruffians will accomplish what they hope to accomplish. It would also leave open the storyline of Silas questing for the Singing rock, thus allowing for a "Return of the King". A nifty offshoot of the main story line indeed. Prequels could be an option too, those dealing with Merra or any of the events previously mentioned (Even Tyrlong, or Rolo, or Silas).
A second option would be to create a sourcebook. Something you could release along with maps, information about each people's, culture, temperaments and relations, along with the same style of art utilized in the game.
For a third option the more adventurous could find themselves an actual Ghost Of a Tale world through the form of a Tabletop RPG. However, I would advise against using the game's title's acronyms, GOAT, as it may relay the wrong image That being said, you have enough material, art, and a stable well developed historical canon to work from. The only piece missing would be the map and the actual game system itself. One could always adopt a system and simply create a sourcebook for it if you wanted to do less work.
These avenues could produce some extra revenue, but also create and a expand a larger fan-base. Something like a tabletop RPG could extend to forum gaming, which still seems to be popular enough, and may serve as an interesting goldmine for ideas, or as a place to "playtest" some scenarios and ideas you may have.
Thanks again for the game, it was a real pleasure to play, as it was a real work of art and craftsmanship.