I love the thumbs up feature and would not like to see it go away. I feel it would be the rare occasion that a moderator would have to over ride a thumbnail in the database.
I don't know about anyone else, but in the sempervivum we have the first/original photos for some cultivars that were pretty poor quality, because that was all we had at the time. I can say this because most of them were mine. So that's all there was to give thumbs up to, so people were choosing the best one out of the batch of bad photos. I have been removing my poor quality photos now that we have some very nice photos entered by a lot of great people here at ATP. I think this will all even out once each plant entry is filled with photos.
But I still think it's a good idea to have the ability to over ride if it's necessary.