As a community of artists - or if you're firmly in the "Poser is not art" camp, a community of creative types producing artfully-created  non-art ;-) - I think there is an aesthetic argument to be made.

Unless your render is perfectly square and not too much larger than the thumb itself, the thumbnail has a different set of aesthetic constraints from the main render. It must be square. It must be small. For a highly detailed, 16:9 format render, these constraints alone would make a cropped thumbnail the compelling choice.

Any artist knows that the choice of format affects your product. If I were shooting a video, I'd certainly do it differently depending on whether it was meant for theatrical exhibition or consumption on a cell phone screen. Change the size and the level of detail, and you've changed the rules, at least in the visual arts.

Also, there's the advertising angle. The galleries are a kind of marketplace, though the currency is attention not dollars. Marketplaces imply (some would say require) advertising. And as with all advertising you have a continuum of quality, from sublime to crass, from straightforward to deceptive. And a well-known tenet of advertising is that if it gets your attention it's working, whether you end up liking the product or not.

• Jimdoria  ~@>@