- Check out Soda here: https://github.com/buymeasoda/soda-theme
- There's also the Phoenix theme here: https://github.com/netatoo/phoenix-theme
- I'm a fan of Sublime Magnificent, found here: https://github.com/kuroir/Sublime-Magnificent-Theme
- Here's another one called Nil: https://github.com/nilium/st2-nil-theme
I'm sure there are a bunch more out there, these are just the ones I could recall off the top of my head to search for. You may just want to use one of those, but if you still want to theme it yourself, just dig into the files. You'll see it's all json, xml, and png's.