Hello,
I have override footer report like this :

<template id="external_footer_custom" inherit_id="report.external_layout_footer">
<xpath expr="//div[@class='footer']" position="replace">
    <div class="footer">
	    <div class="text-center" style="padding-bottom:15px">
            <img style="display:inline-block;margin-right:30px" src="/mikeb_modele/static/images/eco-artisan.jpg" />
            <img style="display:inline-block;margin-right:20px" src="/mikeb_modele/static/images/rge-sol.png" />
            <img style="display:inline-block;margin-right:20px" src="/mikeb_modele/static/images/rge-pac.png" />
            <img style="display:inline-block;margin-right:20px" src="/mikeb_modele/static/images/rge-pv.png" />
            <img style="display:inline-block" src="/mikeb_modele/static/images/rge-bois.png" />
            </div>
	<div class="text-center" style="border-top: 1px solid black;font-size:0.6em">
	Adresse du siège: <span t-field="company.street" /> <span t-field="company.zip" /> <span t-field="company.city" /><br />
	<span t-field="company.partner_id.comment" /><br />
	Tel: <span t-field="company.phone" /> - Fax: <span t-field="company.fax" /><br />
	Siret: <span t-field="company.siret" /> - Ape: <span t-field="company.ape" /><br />
	TVA intracommunautaire: <span t-field="company.vat" />
	</div>
	<div class="row" style="margin:10px 0px;"></div>
    </div>
</xpath>

Thank you!