I've made a change to my template. How do I force all the HTML to be regenerated?

find <target-directory> -name "*.html" -delete
terbium <source-directory> <target-directory>

Why doesn't Terbium generate thumbnails for my video files?

The simple reason is that this introduces far too many additional dependencies for what is probably an infrequent case. I use mplayer to generate the thumbnail images. In the terbium/tools directory there is a sample shell script based on what I use. It is intended as an example, and no testing in a distribution environment has been done.

Why doesn't Terbium use Lightbox or some other Javascript library for fancy transition effects?

The most immediate is that when I wanted a gallery generated, I didn't want fancy effects. I wanted the output to be simple, clean and fast. Lightbox and some similar libraries tend to have licenses that are not GPL-compatible, which is a technical hurdle. All that being said, it is quite probable that in the future set of "heavier" templates will be developed. Input/help on these is most welcome.

Terbium displays all items (video, images, audio) on a single page. Is having x per page possible?

As the code exists today, this is not easily possible. It is something I have in mind for a future version, however. There may in fact be two different approaches to this.

Why doesn't Terbium support displaying by tags or searches?

The initial requirements (low complexity, simple, clean, fast) did not include searchability, or generation of arbitrary pages based on meta-data tags. This is an idea for a future version, but is likely dependent on using a richer datastore than just .properties files.