There is a balance to be struck between being too easy and too elusive. For those putting in the time and effort in to come up with the puzzles, it can be somewhat unsatisfying to see them solved quickly, but this is what helps the thread maintain momentum and go forward.
Most importantly, it is fun for those playing the game. And for all games, being fun for the players is key to success.
One possible solution is to pick several screenshots, of different difficulties, but ultimately, it’s always the part that is too difficult that kills the pace.