I've been designing a few postcards at work lately and was in search of a good free postcard mockup to display them on our portfolio, but I was unable to find one. So I made one! It's definitely not perfect, but I think that it gets the job done. And you know what? I'm going to give it away to everyone for free. Hope it helps someone. Enjoy :)
You can download the editable Photoshop file (psd) from this Dropbox link.