Yeah, we were guessing people would do that. However, there aren't that many ways to prevent this from happening. If we make the prizes worse, would as many participate?
I think the general reception has been positive, so we would do this kind of contests in the future too. Then we'll be sure to take any feedback into account and try to make it work better for everyone.
No, you can't prevent this from happening, but you could make a "Terms and conditions" document where if the admins saw this behavior with proofs (like an order in Voters-Club or other system), you could delete the pic, not pay the prize, or cancel the contest, for example.
Anyway, it was nice to see our works in your FB page Tnx!