image in <bookinfo>

Hi,

I try to put a logo in the <bookinfo> for html output. According to  
the <bookinfo> tag reference, MediaObject is a children of BookInfo.

I tried as follows:

     <bookinfo>
            <mediaobject>
             <imageobject>
                 <imagedata fileref="img/sun_logo.gif" format="GIF"/>
             </imageobject>
             <imageobject>
                 <imagedata fileref="img/sun_logo.eps" format="EPS"/>
             </imageobject>
             <imageobject>
                 <imagedata fileref="img/sun_logo.ps" format="PS"/>
             </imageobject>
         </mediaobject>
     </bookinfo>

Processing through xsltproc works with no errors, but the graphic is  
not shown. When I put the MediaObject code in the <book>, the .gif is  
showed.

Is there any xsl customization needed to get this working ?

ManyThanks_rico