Hidden fields... That does't means a big deal in SEO. You should edit the html and add 'description', 'keywords', etc. But the most important is that PR doesn't mean anything at all in this times. As you can see..
demo.chevereto.com has PR4 and is the same script that is available for download, so... Why google doesn't hit me with PR 0?
In the "other script" you have more text, more links, more descriptions. In Chevereto we have almost no text and no
self explained words like "File name: filename.jpg" or "Filesize: xxKb", etc. So, that is where is your SEO issue. You should read this:
http://searchengineland.com/is-hiding-content-with-display-none-legitimate-seo-13643
Since you ask for it, I'm going to put some lines to edit descriptions and keywords in config.php but is just part of the real solution what is change the words in the script, instead of "filename.jpg (200kb)" in SEO English it needs to be "Filename: filename.jpg (filesize: 200kb)" and so on... But that is up to who runs Chevereto, at this time the script is not SEO friendly and is not a real issue for me... As i say to you, you need to make your own self-explained SEO texts.
Since
Chevereto is moving to a paid script , I have in mind really SEO optimization. Featuring self explained words, self generated descriptions, sitemaps, keywords, tags, friendly urls, and a large etc. There is no way to have all of this rich features in the current script because you need db to have keywords by tags for instance. If someone wants to develop some db model for the Free Chevereto (aka NB) I will help with that. In fact, and as i say over and over... I want that the earnings of the commercial script helps to the develop of the free version, that is because the NB has been the core of this project since the beginning.