(Inspired by Sorceress)
First of all, I should note that I had some conflict with this, but decided to split my votes 3 Positive, 6 Neutral, and 3 Negative, so I had to work around that. May change it to 4/4/4 for the next round. My preferences were for themes that informed gameplay first and foremost, and offered lots of options, and were not too complex for a 48 hour period.
Construction – This is probably what would have gotten my last +1 had I had one. It’s a bit generic, but there are lot of possibilities in almost every genre, storytelling style, art style, etc.
End Of The World – Very common, and more of a storytelling theme than a gameplay theme, which is what I think the themes should be about. It’s not bad, though.
Ghosts – I frankly just stared blankly at this for a few seconds before downvoting. No ideas at all. Perhaps others will be less dense, but I’m not feeling it.
Guardian – This could have some interesting storytelling options in my opinion, and it made me think of Halo which is lovely, but in the end it’s like EotW – too broad and too story-based vs. gameplay-based (there is the gameplay interpretation of attack/defense but that’s too limiting imo).
Inverse World – Could be very awesome, but it seems like too much of a challenge to think up and execute a working concept for Ludum Dare, though I might be selling us short.
Mirrors – Too specific. It’s been a long time since I’ve seen an original game heavily using mirrors. I don’t want half our games to look the exact same.
Outer Space – while I love outer space, and it’s a great setting, it’s not a great gameplay concept.
Quarantine – This one I like a lot. You can basically do anything from creating, destroying, or exploring a quarantine, with any character or group of characters, in any control scheme/genre, with no restrictions on story arc or setting (though it might gather a lot of very stereotypical sci-fi/zombie settings, they fit rather easily).
Salvage – Again, very great from a gameplay standpoint imo (though not as good as Quarantine). Trading, collecting, working around, exploring, etc.
Symbiosis – it’s… not bad… it’s kind of like a weird mix of a backstory concept, mixed with the difficult-to-execute gameplay ideas of Inverse World. Though I might be underestimating us once again.
Trapped – Generic and very similar to the recent theme of Escape.
Unstoppable – Something I have a personal predisposition towards, but I like the idea of fighting the inevitable. And you can make basically anything unstoppable – the player, the enemies, the environment, anything affecting the gameplay or story could be the unstoppable thing. Or multiple things could be! Or they could be considered unstoppable, but not actually be such. Lots of meaningful options.