[Viridovix]

Hi DaleDe, that entry is also present:

<?xml version="1.0" encoding="UTF-8"?>
<package xmlns="http://www.idpf.org/2007/opf" xmlns:dc="http://purl.org/dc/elements/1.1/"
    xmlns:opf="http://www.idpf.org/2007/opf" unique-identifier="BookID" version="2.0">
    <metadata>
        <dc:title>My Title</dc:title>
        <dc:creator opf:role="aut">Viridovix</dc:creator>
        <dc:language>it-IT</dc:language>
        <dc:rights>All rights reserved</dc:rights>
        <dc:publisher>USNB</dc:publisher>
        <dc:identifier id="BookID" opf:scheme="UUID">www.usnb.it-16-653113-38132</dc:identifier>
        <dc:subject>Doc Subject</dc:subject>
        <dc:date>2012-11-22T12:37:35.936+01:00</dc:date>
        <meta content="USNB" name="copyright"/>
        <meta content="cover-image" name="cover"/>
    </metadata>
    <manifest>
        <item id="cover-image" href="image/cover.svg" media-type="image/svg+xml"/>
        <item id="cover-page" href="copertina.xhtml" media-type="application/xhtml+xml"/>
        <item id="ncx" href="toc.ncx" media-type="application/x-dtbncx+xml"/>
        <item id="style-bgt1" href="bgtxml1.css" media-type="text/css"/>
        <item id="style-bgt2" href="bgtxml2.css" media-type="text/css"/>
        <item id="front01" href="frontespizio_front01.xhtml" media-type="application/xhtml+xml"/>
        <item id="relpres1" href="relpres1.xhtml" media-type="application/xhtml+xml"/>
        <item id="articolato1" href="articolato1.xhtml" media-type="application/xhtml+xml" />
    </manifest>
    <spine toc="ncx">
        <itemref idref="cover-page" linear="yes"/>
        <itemref idref="front01"/>
        <itemref idref="relpres1"/>
        <itemref idref="articolato1"/>
    </spine>
    <guide>
        <reference href="copertina.xhtml" title="Copertina" type="cover"/>
    </guide>
</package>

I think that probably ePub doesn't support SVG for thumbnails...