Oh, it's actually a very good idea. You need to promote it via Twitter, Youtube and other socially-driven platforms. I'd make the 1st step (upload your photo) more prominent. It will show your visitors that this is very simple. And they like it simple! I didn't have the time to go through the process, but what happens once I've made the cover? Can I save it? Can I send it as a e-card to someone? Will it remain hosted on your site and can I hot-link it from my forum profile or anywhere else? Think about engagement and how can you make people come back and share their covers with friends. Cool idea!!
this creative website reminds me to some of web based services like photofunia-dot-com where you can add your foto to some places, or a website service (forgot the name) that upload two photos to generate a baby photos.