Since you seem to enjoy gallery hacking you might be interested in this if you haven't seen it already, http://nwalsh.com/hacks/gallery/index.html

It might help you implement a mosaicing feature that I would like you to implement :) That is being able to limit the mosaic input to an album and all its subalbums. I have a feeling that this is a pain in the ass because you have to parse all the gallery .dat files for each album and suck out subalbums. Well, the link above has a perl script that looks like it does a lot of that work already , but I don't know perl and don't have the time to learn right now so since I saw that you already have a gallery mosaic script going I thought that you would be a good candidate to work on this :)