If you are having issues uploading an image to one of the paid templates try switching browsers. This is usually caused by an issue in your browser. Sometimes its cache related sometimes its browser version related.
We highly recommend Google Chrome, using a fresh Incognito browser window. If you're still unable to upload the image after switching browsers, we'd be happy to help you out!
Submit a ticket to us, attaching the image you want and we'll be happy to help.