The app is developped for Cozycloud which is a personal platform as a service (= the app is independent from the platform). It has been written with an ODM (JugglingDB) so you can switch the data layer at your will. Also, this is a single page app meaning the server is only a REST API Backbone (and everything allowed to) can access.
For the "skinnable" part, we didn't have time to bring those features but it is something I would love to see!
On a side note, we, at Cozy, have developed a photo management app (https://github.com/mycozycloud/cozy-photos/, demo: https://demo.cozycloud.cc/#apps/photos/) if it can help you in any way! Or maybe you'll like it and contribute to it ;)
My only disappointment was, a full CozyCloud stack VPS, when I emailed one of you guys, required a significant amount of memory (maybe minimum 1024MB, perhaps IIRC 2048MB?) is expensive for VPS, so I am not sure I want to invest in it.
That being said, CC is very cool and I think the future of nerds running their own clouds, and with a hipster environment like Node.js to boot! :-) The CozyCloud guys do solid work, and I want to compliment you for a job well done so far.
A few recommendations for you that I also plan on for myself:
1. Keep the backend 'database' as simple (and portable) as possible. Files and folders is ideal, with metadata stored in the files (in this case probably as ID3,etc tags)
2. Have a simple API to the data so 'rich clients' could be developed that are capable of caching limited sets of data for offline usage.
3. Make the HTML interface somewhat skinnable so people with conflicting tastes to you don't get turned off just because of the style.
4. Focus on a great personal experience before adding lots of sharing features.
Good luck!