>>3323185Isn't that what the original dude you replied to tried to say?
Particular objects, such as taxis their drivers could be a good theme. Even though the theme itself seems to be just an object, with some photo skills you can frame and express the object differently, preferably matching the culture of each area. Or not, if you want to show the mundane taxis as something permanent across cultures.
A certain object as a starting point for a theme is simple and gives you something to work with. You don't have to spend a ton of time chasing it either, you can just focus on all kinds of other subjects and whenever a taxi happens to pass you get a photo of that. It's not very time-consuming to focus on something mundane, so you can capture multiple themes during the same trip.