Hey there. Apologies for the slow reply. I am currently anchored in Phang Nga Bay - one of the locations of Pirate Jam 2020 - scouting good places to take our fleet in March. Spent several days traveling, getting the boat ready, and sailing to get up here before I had a chance to sit down and respond...
For the voting... Yeah, given that we're talking about a free trip to Thailand as the Grand Prize, I too am concerned about people gaming the system. That's why the ultimate decision will be made manually. As for how we'll pick the Grand Prize winner... I imagine there will be lots of submissions from people who are automatically disqualified because they don't have a passport and/or are unable to travel for the required dates. Out of the remaining pool it's going to be more of a "we'll know it when we see it" type of judging. Which means it's not so much about the graphics or gameplay as the impression the thing makes. I like games that make me laugh for being surreal, irreverent, and violently cute (or cutely violent). From Pirate Jam 2019 my favorite game (which made me laugh the hardest) was Eat The Rich.
You can see Eat The Rich here: https://www.pirate-jam.com/pirate-jam-2019 (not that your game has to be anything like that to be considered or to win).
Anyway, if this seems less than helpful... that's probably a good thing. Let's wait until the theme announced and then everyone can have a go at it :)