The reason for three votes is so that the one vote that you might cast for yourself does not screw up the results. There is no way other than honor to implement that system.
I am going to say that if I thought my shot was one of the best three then I would vote for my shot. You will notice that my shot is one of only two that have no votes so I am just going to say that I am an honest voter. Two of the three current leaders are shots that I voted for. One is not. That means that so far a majority agree with me on two of those shots. The one that everyone didn't sure doesn't look like it is going to make the cut.
What I am saying is that if I voted for my own shot then I would have cheated one of the more deserving, in my opinion, shots out of one vote. But I would still be sitting here with one single vote. I knew when I posted my shot that it was not going to win but I operate by my own set of unwritten rules and I won't post my best shot from the last year or whatever. I challenge myself to get out and take a shot. That is just me but I am not asking to make it a rule. I am just saying that these are the ways that I operate. If we "suggest" that you not be allowed to vote for your own shot then we will all have to trust that everyone will follow that suggestion. I am not comfortable with that honor system as I am thinking that I might be the only one to play by the rules.
Just my humble opinion.