I'm now (more or less) working together with zsbzsb to make things going and any suggestions are more than welcome.
It looks like one of the crucial troubles is low awareness about the jam in general which leads to low participation etc. No big thing was build overnight and my impression is, we should push the promotion a bit, make things clear and predictable as in there's a SFML Game Jam x times a year around this and this time, so people can expect it, note it into their (mental) diaries, prepare for them and just get used to the idea of doing the jam that time of the year. Just what LD and GGJ does. Periodicity, promotion, awareness, preparedness.
It's honestly one of those circular problems. Not many games are done in the jam because not many people care about it at the moment and not many people care about it at the moment because not many games are done. And as the games won't make themselves, it's clear it must be cut at the people awareness part.
About the theme, voting, etc. Well, this can be really hard thing to crack. At most jams I've been to, the general feeling about the final theme was "why this one, there've been much better ones on the list", but yeah, that's democracy. About more people voting than delivering, I don't think people vote just to have games served to them, but people might vote, try to develop but in the end miss the deadline or generally screw. That happens and there's probably not much that can be done about it. We can make the timeframe a bit more benevolent (say 96h, from Friday 12 AM UTC to Tuesday 12 AM UTC) so people can better plan their time and not be affected that much by their timezone, but in the end, there will always be someone, who dislikes the setting no matter how it is.
My experience about much longer jams is bad in general. Once you have plenty of time, things get postponed, motivation and drive goes away after the first few days, work, family and life gets in the way and then, the jam silently ends. Some projects are delivered, but not many people care at that moment anymore. Some longer jams even embrace the idea, putting weight on the personal achievement and skipping any kind of voting or presentation in general besides "here's the list of games made, have fun".
Themes can be redacted a bit in the current system, but some clear key would probably be good, so people don't have bad feelings about their theme put down before voting without clear reason why. To broad might be a good marker along with offensive, nonsense (asdfghjkl) and probably other flags.
Completely different question is, how large really SFML user base is and how much of us are even interested in doing game jams. Also if those numbers might get better with enough promotion, periodicity and care in general.
My feeling from countless hours of chat on IRC is, there are people, who'd like to give it a try. Some might be more experienced than others, some might fail to deliver (hack even I failed to deliver more than one time, that happens) and there are other people who might try if motivated. We should be able to build and cultivate a community around this jam, if we give it some care. And that doesn't mean one run, that means some continual work and active and positive approach from everyone from organizers to participants. Maybe this run will have a really bad theme. Maybe we will end up with very few games. The point is to still take it positively, as there were new games developed that wouldn't be otherwise, there were lessons learned, experiments tried and of course fun doing so.
The goal is to have the people come next time and bring friends. To motivate people idling around IRC and Forum to come and try. Even if they do just another flappy bird clone, it counts. Lessons learned, fun delivered. Because if you can do something trivial this time, you should be able to do something bigger next time.
For the looked at part, we might promote the games through the jam channels (mostly twitter right now), but again that would need some clear key so no one is able to spam it and everyone has the same chance to get attention. First idea out of my mind would be have participants tweet about their game once they submit and retweet those posts based on special hashtag, one tweet tops for each project at time authors decide (by tweeting about it with the hashtag). Sure, we're nowhere near the LD size and popularity, but big things aren't built overnight.
I know the competition is large. Ludum Dare, Global Game Jam, hundreds of small jams running all the time. We also cater only a specific segment of gamedevs, the SFML users. But I still think this might be viable, if we want it viable. There are more than 10000 registered users on this Forum. SFML is mentioned around the web and compared to SDL, Allegro and other popular libraries. Of course it's not Unity (meant in user base size), but the potential is there.
It also goes hand in hand with SFML popularity itself. More people using SFML, more people potentially interested in this jam. More people interested in this jam, more people (considering) using SFML.
I'd like to give it a try. We might fail in the end, but that's true about most things worth the effort. Even if we fail, hopefully there will be some people having fun in the process.
tl;dr;
Let's try and see. There are things we can try and every problem has a solution. IMHO all we need is better awareness and will to continue even if we don't get big results instantly. After all it's about fun and trying new things.