|From GT: Starports|
While the Black Ocean of Space is far different from the Blue Oceans of Earth, the workings of both seaports and starports are going to be similar. Cargo moved, and an interface between lands. The crew of a ship after a long journey is going to be looking for something different. Stevedores and longshoremen will move cargo. While some of the encounters are more early modern in origin, like a fortress firing a noon-gun, even a starport may have some sort of daily ceremony, if only to break the workday up. A side-show, as seen in the opening of The Message, is another thing you could have as a random encounter.
One of the themes I find implicit in Traveller is how humanity has not changed much over time. A setting over three thousand years in the future, where wars are still fought, societies divided and fighting among themselves, and yet still curiosity to grow and change. So I feel fine in borrowing from fantasy settings. In this case, a place where societies meet is going to be relatively similar over time. As for it being a D20 table, are you really a role-player if you don't have a collection of polyhedrals?