Images stored in attributes of type Picture are displayed on object forms. Images can also be stored in attributes of type Document (like files of any other type). In both cases the user can upload an image via an object form.
Also, images can be uploaded into database by rules (see the process that creates members and items during initialization of Library sample application). Alternatively images can be imported in a hexadecimal format from a CSV file (see the product step in the initialization process of Ordering sample application).