There are 3 topics here:
- rules - what if everyone just sends a minimal amount to each of 30 addresses. They will simply split the jackpot, the lottery becomes a giveaway.
- provably fair - photo is not a proof. Randomly select a winning address right now and post here the hash sha256(address||secret), when the round ends post the secret.
- trust - this one is difficult...
I also was trying (kind of experiment) to host a lottery. Rules and provably fair were not a problem.
But the trust... Yes, there could have been winners and losers, but even with +EV (because of 'jackpot') there were not many participants.
Maybe the big prize can solve trust concerns, I can't yet afford 5 BTC giveaway.

Here we have a clear win scenario. Doesn't matter which address will win.
But for those who want to test their luck just post the hash as a fairness proof.
Then we'll see how trust and 5
BTC correlate.
Good luck!
