This is a smart semantic solution, and might be a better defacto than tables, though easier to layout, position and produce.
Now, using definition lists might be somewhat strange, but as the W3C points out, it's great for other purposes too. Usage is easy: <dt><img src="img.jpg" /></dt><dd>Caption</dd>. Easy as pie.
Good thing is, the captions are semantically pretty nice. Turn of your style sheets to see what I mean – it works.