CREATE TABLE image {
    item_id    INTEGER NOT NULL,
    picture    OID,
    CONSTRAINT image_pk PRIMARY KEY(item_id),
    CONSTRAINT image_item_id_fk FOREIGN KEY(item_id) REFERENCES item(item_id)
};

##</code><code>##

INSERT INTO image VALUES (3, lo_import('/tmp/image_name.jpg'));
SELECT lo_export(picture, '/tmp/image_name.jpg') FROM image WHERE item_id = 3;
to delete:
SELECT lo_unlink(picture) FROM image WHERE item_id = 3;