In general you cannot place images to particular places of document layout via PD4ML API or with resource loaders.
You define your document layout using HTML and the images positions are defined by a locations of tags.
If you plan to load images from a database, you may define your own image loading protocol. For example:
Your custom resource loader should parse the string “database:table=images;key=4711” and perform a corresponding request to the database (using the key value to locate a proper image) via JDBC (or similar).