Ghost is a great blogging platform. It's fast, it's open source, and it simple to use. However, as a on-again/off-again user of Ghost (I have a habit of switching to Wordpress sometimes) the one thing that drives me crazy is the lack of theme updating that takes place.
If you do a simple Google search for "Ghost themes" you'll see all sorts of results, however, only about one or two of those themes seem to work on the most up to date version of Ghost. Most haven't been update in the last several years.
Here are a few (not all) themes that actually work as of v. 1.24.4 (current version at writing is 1.24.8). Happy Ghosting, 'er, blogging!
These are in the order in which I like them. The link is above the picture.
arabica (version 2.0.1); below ↓
Ghostium (version 2.3.2); below ↓
scriptor (version 1.3.0); below ↓
casper (version 2.3.3); below ↓
Mention (version 1.0.0); below ↓
attila (version 1.7.0); below ↓