In the latest game jams, the themes have always been "mechanic-oriented". "Delay the inevitable", you need to implement some delaying mechanic. "Every 10 seconds", you need to have a mechanic that happens every ten seconds. "Harvest", well harvesting might be part of your mechanic here.

I would like to try to promote themes that are actually thematic and not constraining the design. This is why I am promoting strange machines as I think it has an extremely high level of creativity potential and I'm looking forward to see what machines are created!