In celebration of the stable release of Gatsby Themes, the Gatsby Theme Jam contest was announced, inviting participants to create and submit their own Gatsby Themes by July 31st, 2019, with all entrants receiving a limited-edition mug or t-shirt and two winners earning a trip to a Gatsby Days event. Gatsby Themes are installable packages that streamline the setup of a site's styling, components, plugins, and configuration, allowing for easy updates and swaps. Participants can build new themes or expand existing ones, such as the official blog or notes themes, using resources like Gatsby's documentation, a free Egghead.io course, and a "Learn with Jason" session. Contest submissions must include links to their GitHub repository, npm package, and demo site, and will be judged on criteria such as code quality, accessibility, performance, documentation, and creativity. Further details and resources are available on the contest website, themejam.gatsbyjs.org.