Use a pattern fill (with the image you want) for the region (doesn't require masking)
or
Use a pattern fill on a rectangle that uses a mask with the region in it
<svg xmlns="http://www.w3.org/2000/svg"
xmlns:xlink="http://www.w3.org/1999/xlink"
viewBox="0 0 1000 360">
<defs>
<pattern patternUnits="userSpaceOnUse" id="pat1" x="10" y="10"
width="425" height="319">
<image width="425" height="319"
xlink:href="http://designm.ag/images/0709/wood/71.jpg" />
</pattern>
<text id="txt1" y="100" font-weight="bold" font-family="Verdana"
font-size="100">Some Text</text>
</defs>
<use width="1000" height="400" xlink:href="#txt1" fill="url(#pat1)"/>
</svg>
Here's a fiddle showing how to do a simple pattern.