Hi! I'm the head of the UX steering committee.
Most of the visual components are made in qml and C++.
The OS is break down into different aspects: the base system, services, apps, etc. therefore there's no «global package» you can install to modify. If you want to shape the look of an app, you must edit its qml code. If you wanted to modify the notes app you would likely want to edit its qml code.
To shape the indicators is a bit more complex task as each of the indicators has its place and it's written in a different language: you can find their code here
As for scopes, we are using the last work done by Canonical and they removed them by several reasons.
Maybe, if you want to show your concept is better to make some sketches or mockups. Depending on your skills you can use Inkscape, GIMP or hand drawings.