After posting my question here I solved it by myself:
In portalblocks.php find the following code:
echo '
<table class="sp_auto_align">', $direction ? '
<tr>' : '';
foreach ($items as $item)
{
echo !$direction ? '
<tr>' : '', '
<td>
<div class="sp_image smalltext">', ($showLink ? '
<a href="' . $item['topic']['href'] . '">' . $item['file']['filename'] . '</a><br />' : ''), '
<a href="' . $item['topic']['href'] . '">', $item['file']['image']['thumb'], '</a><br />', ($showDownloads ? '
' . $txt['downloads'] . ': ' . $item['file']['downloads'] . '<br />' : ''), ($showPoster ? '
' . $txt['posted_by'] . ': ' . $item['member']['link'] : ''), '
</div>
</td>', !$direction ? '
</tr>' : '';
}
echo $direction ? '
</tr>' : '', '
</table>';
Replace by:
echo '
<marquee><table class="sp_auto_align">', $direction ? '
<tr>' : '';
foreach ($items as $item)
{
echo !$direction ? '
<tr>' : '', '
<td>
<div class="sp_image smalltext">', ($showLink ? '
<a href="' . $item['topic']['href'] . '">' . $item['file']['filename'] . '</a><br />' : ''), '
<a href="' . $item['topic']['href'] . '">', $item['file']['image']['thumb'], '</a><br />', ($showDownloads ? '
' . $txt['downloads'] . ': ' . $item['file']['downloads'] . '<br />' : ''), ($showPoster ? '
' . $txt['posted_by'] . ': ' . $item['member']['link'] : ''), '
</div>
</td>', !$direction ? '
</tr>' : '';
}
echo $direction ? '
</tr>' : '', '
</table></marquee>';