Yet another idea:
Ability to embed album via iframe generated code.
So, lest's say we have albums. It would be good to have the same option we have on Facebook nowadays - get embed code.
I think iframe is the easies way to embed such album in regular "Custom HTML" module.
Imagine, admin can embed user or group gallery (which is an album in fact) into content of regular Joomla page.

Also you may consider content plugin doing the same thing in articles or Custom html module too.
Let's say I'm writing regular article via joomla cms or even using EasyBlog and I want to embed not only single picture, but have a nice gallery
It would be enough to put into content something like {esalbum ID_OF_ALBUM} and voila - we have cover picture embedded.
Clicking cover pic should bring up an usual pop-up (lightbox) with standard controls we have in albums