Thank you for the idea.
Firstly, as it has been mentioned many times before, all events are run under my supervision, so I make sure that they are fair and no preferences are given because of the contestant and not because of their submission.
Secondly, not always the most "technically well-made" submission is the best one. We do understand and take into consideration that not all of the players have outstanding drawing/digital skills, however we do want to give everyone the same chances of participating and winning. So perhaps some time a work is not the best looking one, however the idea behind it might be better, thus it is given a higher place in some contest.
Thirdly, the way of chosing the winners differs from event to event. In some cases Jesters are the judges, in some events Administration is in charge of choosing the winners. Sometimes we give players the chance to vote for other players works. The voting systems also change from event to event, we try to find the best way to choose the winners the fairest way possible.
Back to your idea, even if players send their entries secretly, the information will be leaked anyway, so it doesn't make much sense, aside the fact that it would require much more time and effort to do things this way. However, the concept is interesting, we might aswell try a system similar to that during some event.