Any idea or improvement to suggest?
Shout!
Overall I really liked the jam, so I don't have any complaints or major change suggestions.
One small suggestion is to clarify on the jam page what you mean by "polishing". There was some confusion over what qualifies. Some people had a more strict interpretation meaning only bug fixes and very minor changes, whereas I would have prefered a more open interpreation meaning you could add some things like sound effects, particle effects, UI art, difficulty balancing, etc. Either way some guidance would help.
One of the most professional Jams I've been in, this was a really fun experience and I hope I'm free to do this again next year, the 'polishing' week was quite vague, in my opinion i don't think there should be a polishing week because there will most likely be people confused no matter how in depth the guidance of what is and isn't polish, to avoid confusion I would just either make the jam 2 weeks to keep the 'polishing' week around unofficially to avoid confusion and let people just work on the game as if it was a 2 week jam or just leave it as a 1 week jam.
I really liked the live streams too, this whole thing was great, thanks for hosting it! :)