storage_thumbnail/data/ir_parameter.xml
<?xml version="1.0" encoding="utf-8"?>
<odoo noupdate="1">
<record id="storage_thumbnail_backend" model="ir.config_parameter">
<field name="key">storage.thumbnail.backend_id</field>
<field name="value" ref="storage_backend.default_storage_backend"/>
</record>
</odoo>