Themes allow you to change the look and feel of your Drupal site. You can use themes contributed by others or create your own to share with the community. Contributed themes are not part of any official release and may not have optimized code/functionality for your purposes.
You can also create a sub-theme of an existing theme. A sub-theme inherits a parent theme's resources. Read more about Sub-theme structure and inheritance.
You can also view a full index of themes listing only their titles.
SeaserWebBIR theme is a Semantic UI based Drupal 7 theme. The theme is dependent semanticui base themes. Its very light weight with modern look and feel. Multipurpose clean layout and light weight code.
Parallax zymphonies theme is single page responsive theme. This theme suits for any type of personal website, corporate, business, marketing etc. This theme is completely free and contributed by Zymphonies team.
Startup theme by Whywebs Drupal8.info
Powerful, yet simple, HTML5 starting theme with a responsive, mobile-first grid design. If you are building your own standards-compliant theme, you will find it much easier to start with this theme than to start with Zen or any other dependable themes. This theme has Lots regions, templates and features that you will always use.
UIkit is a lightweight frontend framework with a comprehensive collection of HTML, CSS, and JS components. It is a great alternative to other frontend frameworks, plus is very lightweight and provides a lot of useful tools for customizing with very little requirements.
So why bring UIkit to Drupal? I wanted a frontend framework that is responsive (mobile-first), easy to use, lightweight, and has better semantics than other frameworks. UIkit meets all of these requirements.