The advantage of both stickers and subscriptions over advertising is that you don't need a sales team or the tech for serving ads and providing analytics.
The WhatsApp system of $0.99 for each year after the first would be one option.
One thing I'd really like is the ability to buy photo books, journal, those sorts of things, made from the photos I take, and information I provide in checkins and updates throughout a journey, holiday, etc. It would be great to get home from a trip having checked in to everywhere, taken photos, posted thoughts and feelings, etc, and get the whole thing in a nice big physical book similar to the ones iPhoto in iLife can produce.
That being said, stickers seem to work. Line makes 30% of it's revenue ($17M in Q1 2013) from stickers. More here: http://start.toshiba.com/news/read/category/Business/article...
The advantage of both stickers and subscriptions over advertising is that you don't need a sales team or the tech for serving ads and providing analytics.