Look around

[Eddi]

But creating additional images for all current objects is quite a big project, not to mention all the content that doesn't come with the game by default;

yes, that is the entire problem.

if you start the infrastructure to both accept additional images when avaiable and already offer a rudimentary functionality that gives a taste of how things could be

the problem is, it cannot work properly. people don't care about the 95% where it does work, they care about the 5% that don't work.

traditionally, the worst part of these 5% are airports. getting a solution for rotating airports is under development, but finishing it is already taking ages. The next problem are irregular industries/houses. [basically everything larger than 1x1]

[Yexo]

getting a solution for rotating airports is under development, but finishing it is already taking ages.

The code supports it already, I'm willing to code any graphics that are produced (and licensed as gpl or cc) but so far none has drawn rotated airport graphics.