About dpoll I understand that you have to go, log in to your profile to be able to vote, I don't know if everyone is willing to take that many steps.

I think we need to change the system a little bit, maybe even make a post about it, and leave in the comment also the link to the post along with the image, that way we could reach more users, even give reblog to the winning posts, so more people will know about the contest.

Based on the above, a manual curator will be needed.

You could set a time window to participate of 5 days, after posting the contest we can participate for 5 days, that way two days are free for the curator to decide the winner.

That's what I can think of for the moment haha, I'm very sleepy because I've been a bit busy these days.