The images you upload into Prime Service Catalog are not stored in a folder in the application server file system. They are stored in the Prime Service Catalog application database, so there is no "folder" you can access directly.
In Prime Service Catalog 10.1 or later, you have the ability to reference images via a URL, so they do not have to be stored in the Prime Service Catalog application. It also allows you to use content caching technology for these images to speed up page load.