Brilliant explanation and tips all the way through this thread, Sasha. Amazing!
Here are some more examples that might help explain how the cropping works @teabreaks.
This is an ACEO that's been photographed with some props to make a 'landscape' shaped image rather than a square. The seller has uploaded the original photo and it displays like this in the listing:
When the image is displayed in shop view, search results or gift guides etc, it is automatically cropped to a square (we don't do it manually - it's just a software thing). The same pic of the ACEO looks like this when it's displayed in those views as a square:
Because the actual ACEO is placed in the central part of the image, it works really well both on the listing and seen in the square window. It's a clever way to get around the whole 'how to fit a rectangular artwork in a square window' problem
This is another example showing an ACEO displayed in a frame, and how it looks in the actual listing and in other views.
The original photo of the ACEO portrait (which is a photographed in an upright rectangular frame with the glass taken out):
How it looks in the square window in the 'Collections' section of her shop:
Here's Sian's shop if you want to see more examples https://folksy.com/shops/siansburys
Hopefully that helps a bit too. Maybe the whole cropping thing needs a blog post to explain more? Maybe you could write it, Sasha?