Short answer is yes. I love a good theme and the more choices for users the better. Longer answer is maybe. There's some criteria for being added to the dropdown, which includes ensuring the theme is usable with default site functionality (markdown functions as intended, posts highlight when selected, homepage layout is fine, etc), selecting a syntax highlighting theme that matches the theme's style and is readable, and providing an appropriate logo for the homepage. If you have a theme to submit, you can post it here on /site/, or e-mail it to the administrators. I can be reached directly at codexx (at) cock (dot) li.