The lack of preview thumbnails with Transfer.it is admittedly a drawback, but all that is needed is for the uploader to create their own preview and drag and drop it to Image upload. I normally consider it a basic courtesy to provide thumbnails, but since I was just filling in a couple of gaps for Westpier I neglected to on this occasion. Sorry 'bout that.
Many forums make it a rule that all uploads must be accompanied by thumbnails, so possibly that should be the case here. I'd certainly support it - as I say, it seems to me a basic courtesy. But others may differ. Since a Thumbnail Generator has been thoughtfully provided in the menu above (Xenon spoils us) it shouldn't be a problem for many files, though .wmv, .avi and .rm files are not supported - so perhaps that needs to be addressed first.