I’m a big fan of Looker, but I’m not a fan of code editors with a white background. I’m sure I’m not the only one 😄 And the default font size is a bit small on my 4K monitor. Unfortunately, Looker does not have any feature yet to customize the IDE. But hey, good news, this is a web app. We can easily override CSS!
As I didn’t find anyone sharing this previously, I thought I would. The customized styles are based on the popular Solarized Dark color scheme with a bit of customization. I also set Inconsolata as the default font (my favorite development font), and increased the font size to 18px.

Note: This was done quickly, it’s not perfect… Feel free to refine, and post your thoughts/improvements here.
HOW TO:
1- If you don’t have one already, install a browser extension that allows you to override styles (such as Stylebot for Chrome).
2- Add a rule for your Looker instance URL, copy the styles found on the Github repo, and customize to your liking!
3- Enjoy!
POST EDIT 05/24/18: Updated stylesheet to reflect changes discussed below.
POST EDIT 04/04/19: Updated post to link to Github repo.