Out of curiosity, is there a reason why we can't set themes on sub-albums? For instance, I have two main galleries, one of audio and one of visual stuff, I use two albums for that with varied themes, but was then thinking of further categorizing my visual category into others like scenic/portrait/etc and would like to be able to set themes accordingly.

Was it just something never looked at? Or is there something technically limiting at this time?

The question has been asked before. And the answer is obvious--of course there is a reason. The overhead of allowing themes, management, etc. on any but the top level albums is not worth the benifit.