Linesymbolizer SLD For geoerver using SVG imags

I want to create a linesymbolizer which is consisted of a SVG (or png) image that is repeated along line.I have used this code but it does not show the image,Can some one please gives me some hints,

    <?xml version="1.0" encoding="ISO-8859-1"?>
<StyledLayerDescriptor version="1.0.0" xmlns="http://ift.tt/1eR7n4M" xmlns:ogc="http://ift.tt/KDbkOK"
  xmlns:xlink="http://ift.tt/PGV9lw" xmlns:xsi="http://ift.tt/ra1lAU"
  xsi:schemaLocation="http://ift.tt/1eR7n4M http://ift.tt/1wHS1ef">
  <NamedLayer>
    <Name>tt</Name>
    <UserStyle>
      <Name>tt</Name>
      <Title>tt distribution</Title>
 <FeatureTypeStyle>
     <Rule>
       <LineSymbolizer>
         <Stroke>
           <CssParameter name="stroke">#0000FF</CssParameter>
           <CssParameter name="stroke-width">1</CssParameter>
           <CssParameter name="stroke-dasharray">10 10</CssParameter>
         </Stroke>
       </LineSymbolizer>
       <LineSymbolizer>
         <Stroke>
           <GraphicStroke>
              <Graphic>
                  <ExternalGraphic>
                    <OnlineResource xlink:type="simple" xlink:href="palm_fill.png" />
                    <Format>image/png</Format>
                  </ExternalGraphic>
                  <Opacity>
                    <ogc:Literal>1.0</ogc:Literal>
                  </Opacity>
                </Graphic>
           </GraphicStroke>
           <CssParameter name="stroke-dasharray">5 15</CssParameter>
           <CssParameter name="stroke-dashoffset">20</CssParameter>
         </Stroke>
       </LineSymbolizer>
     </Rule>
   </FeatureTypeStyle>
   </UserStyle>
  </NamedLayer>
</StyledLayerDescriptor>