How to win a challenge?

I'm trying to win a challenge here, have already quite a few top 6 positions,

but no number one yet There are some really interesting observations to be made.
Your picture needs to be very clear and understood right away in thumbnail size.
For example, I submitted my Venice photo, which is quite unusual
for the amazing clarity of the mountains seen behind the roofs, but
you need to open the image to really appreciate it. People clearly voted
without opening, so this picture failed completely.

http://www.dpreview.com/challenges/Entry.aspx?ID=202577

What other rules do you think are important to follow?

Andrew