in deiner details.html findest du recht weit unten:
<table width="100%" border="0" cellspacing="0" cellpadding="3">
<tr valign="top">
<td class="row2">
{if prev_image_name}{lang_prev_image}<br />
<b><a href="{prev_image_url}">{prev_image_name}</a></b>
<!-- <br /><br /><a href="{prev_image_url}"><img src="{prev_thumb_file}" border="1"></a> -->
{endif prev_image_name} </td>
<td align="right" class="row2">
{if next_image_name}{lang_next_image}<br />
<b><a href="{next_image_url}">{next_image_name}</a></b>
<!-- <br /><br /><a href="{next_image_url}"><img src="{next_thumb_file}" border="1"></a> -->
{endif next_image_name}</td>
</tr>
</table>
das ist die Anweisung vorheriges / nächstes Bild
das willst du von unterhalb nach oberhalb haben, also nimmst du es unten weg
und fügst es z.b. zwischen/nach (wie es dir gefällt):
<b class="title">{image_name}</b>{if image_is_new} <sup class="new">{lang_new}</sup>{endif image_is_new}
<hr size="1" />
{if msg}<b>{msg}<br /><br /></b>{endif msg}
<div align="center">
{image}
{if admin_links}<br />{admin_links}<br />{endif admin_links}
wieder ein!
fertig, das wars