Here is something which should work... it is not a form scrollbox but it is a box which scrolls lol.
CODE
<div style="width:200px; height:500px; overflow:scroll;">
<!-- Put your table in here -->
</div>
Change the width and height how you want. As for your question of putting the over another image; you could change the style so that box has a background image like this:
CODE
<div style="width:200px; height:500px; overflow:scroll; background-image: url(images/filename.jpg);">
<!-- Put your table in here -->
</div>
You can do whatever you want with that div too... as long as you have basic HTML and CSS knowledge.