Well you can follow this thread to get idea about how you can preview an image while uploading. It’s a very simple task: https://stackoverflow.com/questions/4459379/preview-an-image-before-it-is-uploaded
And about the refund I’m sorry to say but there’s no policy like this one. If the theme has got any issue & we’re not able to fix it only then we’ll be able to refund you, otherwise there’s no scope for that. Hopefully the link will help you fix your criteria.