One thing I think Ghost is missing right now is a solid mobile experience. I'm working to fill this gap with Quill [1], a native Android app for Ghost with an offline mode, image uploads, full Ghost Markdown support, and a sweet design. And it's open-source :)
Offline support in particular is IMO going to turn out to be an important feature, because I can imagine Ghost's target audience of journalists wanting to publish quick thoughts from places with a spotty connection. Admittedly I haven't actually validated this - building offline support presents an interesting engg+UX challenge, so that was the original motivator.
Feedback has been really positive so far [2], so I'm gonna keep going! Would love to get feedback from HN as well.
[1]: https://github.com/vickychijwani/quill/
[2]: https://github.com/vickychijwani/quill/wiki/What-users-say