My progress with theming this site is slow going, as it's hard to find enough time to actually work on it. I've made some progress with the user profile page, and also customizing colours that are available to be change easily. Progress is good, but it'll probably take forever until this will be "complete". I'll keep at it, as Twig is pretty awesome to use. All in all, PicoCMS is a lot more powerful than I gave it credit for, and you can build some complicated stuff with ease.
I'll keep plugging away, as my next task is to make the menu bar a lot better, and automatic. We'll see how that goes.