I recall seeing them on this website, there are also some tutorials available:
Tutorial for custom TV videos
Tutorial for custom videogames
Custom TV shows seem to be very easy to make, it's mostly about making sure they are installed in the right place (given we don't want to add extra channels but only rely on the existing ones) while videogames are more time consuming to make, but the tutorial is well done so it's about not getting lost.
Slowly moving steps into basic TS2 modding.