Ask HN: What is the best way to monetize Picisto.com?

I'm looking for some ideas on how to monetize http://www.picisto.com.

The site is currently using 3 monetization methods: 1. Banner advertisements 2. "In-app" purchasing (via Picisto coins) 3. Ordering photo prints

Neither of these methods are clear winners so far. There's no specific "content", so we can't target with ads. And no one seems to want to purchase photo prints.

Does anyone have any other ideas on how to monetize this site?

Thanks.