Marketplace App Metadata Guidelines

Additional Requirements for Themes/Site Templates
A theme without content is like an empty house. If you're trying to sell an empty house, it may be difficult for prospective buyers to see its full beauty. However, staging the house with some furniture and decorations helps prospective buyers imagine what the house might look like with their belongings. Liferay's resources importer application is a tool that allows a theme developer to have files and web content automatically imported into the portal when a theme is deployed.
All standalone themes that are uploaded to Liferay Marketplace must use the resources importer to include files/web content to provide a sample context for their theme. This ensures a uniform experience for Marketplace users: a user can download a theme from Marketplace, install it on their portal, go to Sites or Site Templates in the Control Panel and immediately see their new theme in action. You can read more about themes and even find examples in the Developer's Guide.