You can create several divs and do that:
<div style="width:100px; height:100px;">
<div style="position:relative; top:0px; left:0px; width:100px; height:100px; opacity:0.3;"><img src="urltoimage" alt=" " /></div>
<div style="position:relative; top:0px; left:0px; width:100px; height:100px;"> DIV with no opacity </div>
</div>
I did that couple times... Simple, yet effective...