Backgroud Image for Main Slot in Plone

To make  the  Backgroung image shown underneath the main slot in plone.

edit main_template from where  page body text is called.

edit  ---- Start of main content block ----

edit the <div class="documentContent"> tag  & specify the background image to be used.
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<div class="documentContent" id="region-content" i18n:attributes="background-image" style="background-image: url(/portal_skins/custom/images/middle.jpg);">

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