The following shows control and an imagelist placed under (i.e., in the same column as) a poster, to show thumbnails of additional posters. That's not what you want, but shows the use of imagelist. I suppose you would set the height and width higher, and put it in a column wide enough to display six in a row. Poster and the controls would still have to exist, but could be made small and placed elsewhere.
<row>
<column>
<poster autosize="true" stretch="true"/>
</column>
</row>
<row>
<column halign="left" imgctrlcol="true" width="50">
<prevposterbtn/>
<nextposterbtn/>
<addposterbtn/>
</column>
<column>
<imagelist valign="top" halign="left" cheight="100" cwidth="75" autosize="true" space="10">
<border shape="none"/>
<color>$CCDDEE</color>
</imagelist>
</column>
</row>
An alternative would be to use the screenshots container...
<section>
<color>$000000</color>
<row>
<column>
<screenshots cheight="450" autosize="true">
<border shape="none"/>
</screenshots>
</column>
</row>
</section>