Can anyone improve upon this script?

The link is to a simple script that is useful to display all images in a directory.

I am curious to know if anyone can suggest some simple improvements.

Link with source:

http://johns-jokes.com/downloads/sp/images/index.php

.

Using a fieldset is not semantic and won’t validate.
Personally, I would add a counter and clear each row. This prevents long images from overlapping into the next row.