Looks nice. Mock-up for UI would definitely be nice, though I'm not currently considering substantial changes (i.e. adding a search bar that will also change how search results are displayed).
I'd probably wait until it's more feature-complete so it can be better determined how to fit all of the information together. I'm not making big UI changes until then myself, including the custom theming. There is also the need to consider variable-sized buttons and other elements (for multi-language text support). For that, I created a "NinePatch" parser (if you're familiar with android dev where's it's common).
EDIT: In fact, if it supports custom theming, that will probably change how we make the UI entirely. We will have to make things specifically more modular or generic. I definitely don't want to spend time making UI changes now before determining the goal.