<img id="image" name="image" src="" />
<input type="file" name="file" onchange="setImage(this)"/>
</body>
<script language="javascript">
function setImage(obj){
    image.src = obj.value;
}
</script>

------解决方案--------------------
来晚了一步.....
HTML code

<img id="image" name="image" src="" />
<input type="file" name="file" onchange="setImage(this)"/>
</body>
<script language="javascript">
function setImage(obj){
    image.src = obj.value;
}
</script>

------解决方案--------------------
同意

<img id="image" name="image" src="" />
<input type="file" name="file" onchange="setImage(this)"/>
</body>
<script language="javascript">
function setImage(obj){
   image.src = obj.value;
}
</script>