Nirmalya, you will need to edit dndindex.html and general.html files of this theme ( /ow_themes/graphitelus/masterpages/ ) and add hyperlink to your image.

Sorry,

I am using the graphitium theme and I have replaced the masterpages with the graphite + sidebar theme. Still it doesn't work.

Nirmalya,  sorry, I meant graphitium )). It doesnt really matter which theme, the path is always the same /ow_themes/yourthemename/masterpages/ . What do you currently have in the header of your dndindex and general html files?

In the general.html

<div class="body_wrap"><div class="ow_header"><div class="ow_canvas"><div class="ow_page ow_top">{component class='BASE_CMP_Console'}    <div class="ow_logo">            <h2><a href="{$siteUrl}">{$siteName}</a></h2>            <div class="ow_tagline">{$siteTagline}</div>        </div>       {$main_menu}</div>    </div></div><div class="ow_page_container"><div class="ow_canvas clearfix"><div class="ow_page clearfix">    <h1 class="ow_stdmargin {$heading_icon_class}">{$heading}</h1>        <div class="ow_content">                {add_content key='base.add_page_top_content'}           {$content}                {add_content key='base.add_page_bottom_content'}       </div>       <div class="ow_sidebar">           {component class="BASE_CMP_Sidebar"}        </div></div></div></div><div class="ow_footer"><div class="ow_canvas"><div class="ow_page clearfix">{$bottom_menu}<div class="ow_copyright">{text key='base+copyright'}</div><div style="float:right;padding-bottom: 30px;">{$bottomPoweredByLink}</div></div></div></div>    {decorator name='floatbox'}

In the dndindex.html

<div class="body_wrap"><div class="ow_header"><div class="ow_canvas"><div class="ow_page ow_top">{component class='BASE_CMP_Console'}    <div class="ow_logo">            <h2><a href="{$siteUrl}">{$siteName}</a></h2>            <div class="ow_tagline">{$siteTagline}</div>        </div>       {$main_menu}</div>    </div></div><div class="ow_page_container"><div class="ow_canvas"><div class="ow_page clearfix">    {if $heading}<h1 class="ow_stdmargin {$heading_icon_class}">{$heading}</h1>{/if}        <div class="ow_dndindex clearfix">           {$content}       </div></div></div></div><div class="ow_footer"><div class="ow_canvas"><div class="ow_page clearfix">{$bottom_menu}<div class="ow_copyright">{text key='base+copyright'}</div><div style="float:right;padding-bottom: 30px;">{$bottomPoweredByLink}</div></div></div></div>    {decorator name='floatbox'}

Nirmalya, I suggest contacting owner of the graphitium theme.