An image fill for an svg element is achieved through SVG Patterns…
<svg width="700" height="660">
<defs>
<pattern id="image" x="0" y="0" patternUnits="userSpaceOnUse" height="1" width="1">
<image x="0" y="0" xlink:href="https://stackoverflow.com/questions/11496734/url.png"></image>
</pattern>
</defs>
<circle id='top' cx="180" cy="120" r="80" fill="url(#image)"/>
</svg>