Patterns

<svg width="8cm" height="4cm" >
  <defs>
    <pattern id="TrianglePattern"
             x="0" y="0" width="1cm" height="1cm"
             viewBox="0 0 10 10" >
      <path d="M 0 0 L 7 0 L 3.5 7 z" style="fill:red; stroke:blue"/>
    </pattern> 
  </defs>

  <rect style="fill:none; stroke:blue"
        x=".01cm" y=".01cm" width="7.98cm" height="3.98cm"/>

  <ellipse style="fill:url(#TrianglePattern); stroke:black" 
           cx="4cm" cy="2cm" rx="3.5cm" ry="1.5cm" />
</svg>