It's not always possible to crop an image to be square. So it would be great if you could allow us to move/resize the thumbnail, so that if the item is not exactly in the centre of your image or it's not possible to make the image square, you can adjust the thumbnail so that it doesn't look badly cropped and messy.
Currently I'm having to constantly re-crop my image to try and make sure the thumbnail is centered which is very fiddly. Shop images don't need to be square so seems weird the thumbnail is a forced, un-customisable crop of these.