Hi! I'm kind of a heavy Shinyapps.io user, with over 20 apps, and in my experience one of the downsides of the platform is the somewhat slow loading times for sleeping apps.
I believe the apparent slowness of the service could be alleviated by simply allowing users to customize the "Please wait" white screen that appears before an app. Just changing the background color, text color, button color, some custom text and maybe a custom logo would be enough to give users the impression of a proper launch/loading screen, or at least making the loading process less disruptive.
Just my two cents!