I tried to vary things like how zoomed in the picture is, the color and texture of the background (I was biased towards sand background and hand shots as that’s how the majority of seashells are posted) and I might have also messed with brightness and saturation but I don’t remember.
I think I originally talked about it here
https://forum.inaturalist.org/t/how-are-photos-selected-for-cv-training/42403