Chrischall,
If you decide to keep the mod, you might be able to add the following code that you're missing in 1 of those files. (not sure which one since your version is different). Version 4.1.x is loated in skin1/modules/Dynamic_Images/thumbnail_viewer.tpl.
I've looked at Telma Firma's website
http://www.telafirma.com/store/product.php?productid=16138 html source code for version 4.0.x and the code that you're missing is below.
Code:
<link rel="stylesheet" href="/store/skin1/thumbnailviewer/thumbnailviewer.css" type="text/css" />
<script src="/store/skin1/thumbnailviewer/thumbnailviewer.js" type="text/javascript"></script>
Check the path and see if it's correct.
I've tried looking for a mod similar to Telma Firma's but there isn't any great one that stands out. If you do find one, please share.
Thanks,