Is the most liked photo always the one that shows next to the flower/plant information or can it be any photo submitted?

I had always assumed it was just the first image submitted for a particular plant, but I never really gave it much thought.

It's the one with the most thumbs-up, unless in rare cases an admin has selected a different one to represent the main thumbnail. (sometimes a photo of something like seeds or leaves doesn't quite make the best thumbnail to represent the plant, which happened often when the database was first started)