You can change the value in bold red in references.xml. "-10" seems to work, but I don't think it suits the skin.
<control>
<description>default thumbnail panel</description>
<type>thumbnailpanel</type>
<id>11</id>
...
<textXOff>0</textXOff>
<textYOff>1500</textYOff>
...
</control>
Thanks mate, I'll try it out.