No marketing was needed. The app was specifically made just for that single event.

Not being familiar with Slidesome, I thought /that/ was the app you created. Now I see it's just a component you used. Hence my confusion. :P

Ah, I understand your confusion, now. I didn't link to the actual project because it's not active, anymore. I guess I could link to the repo: https://github.com/Leftium/PhotoDrop

Finding a service that integrated with Dropbox the way I wanted probably took more time than the actual development.