There is a ton of 2E and 3E material to use. They skipped over a lot when they tossed together the 5E Planescape.The upper planes are currently useless for gaming potential beyond "paradise invaded."
So what can be done?
So, there are plenty of creatures to fill up the Upper Planes.
Also, unless a PC group is very good, they will find Upper Planes as hostile as the Lower Planes. And more narrow, each plane and each layer has it's own spin on good. So even if you are good, the people and creatures will be at least indifferent to you as your the 'wrong' sort of good.