Theme submissions can be sent through email.
Simply attach the CSS file to the email, and include:
You can also submit your theme in a PR to the repository this is hosted at: roundabout-host.com/steve0greatness/ThemeIndex.
Simply place your theme CSS into a subdirectory under the theme direcotry(this should be your username), then include a bit of metadata in the themes.xml file in the project root.
This meta data should be as follows:
<theme> <title>{Theme Name}</title> <author uri="https://{profile link}" instance="{profile instance}" username="{author username}" >{Author display name}</author> <uri>{pathto/theme.css}</uri> </theme>