Implementations provide for an add-on image framework for a Platform-as-a-Service (PaaS) system. A method of the disclosure includes launching a build container for a build process based on a base image of an application of a multi-tenant Platform-as-a-Service (PaaS) system. The base image provides a core functionality of the application. The method also includes providing a source code for the application to the build container. The method further includes extracting content from an add-on image and assembling an application image using the base image, the source code and the extracted add-on image content in the build container.