In career mode, if you look closely, you can see the name of your Airline in white in the most placeholder font imaginable on the side of your purchased Freelance aircraft.
Often the plane is also white so it makes it hard to see, but that’s about the extent of paint/livery “customization” i’ve seen in the full build. We can easily live without this feature as long as we can select our own liveries when purchasing aircraft, WHICH WE ALSO CANNOT DO.