I have no background in website design etc., so I have no idea how much grief this would cause, but I've often felt that my thumbnail doesn't do my image justice by cutting off all the important or interesting parts of the image. Would it be possible to make it so that the part of the image that is shown in the thumbnail could be chosen by the user rather than by automation?
I don't know if that would be possible, either, but it's an interesting suggestion, and is what occurs on VFXY Weekly Themes if you link a photo from your aminus3 blog. You get to crop the image as you wish, within the limits of the thumbnail's dimensions.
I was just thinking of this yesterday; it would be great for vertical crops if you could specify your own thumbnail. You have my second (or third) on this request!
It would indeed be nice if, after uploading the image, we could move the generated thumbnail up/down or left/right a little to select the preferred view. The panorama I uploaded today has a most boring thumbnail :-)