Most major apps phone home for a big config object (likely JSON) at the start of a run. This would contain things like car icons, etc. You can see an example of this in the 3p Uber API which has a call to get which car types are available at a given geolocation. This API returns not only the vehicle types (Uber X, Uber Black, etc) but also a jpeg icon representing the car. In this way Uber can roll out new car types in locations without a client side update.

I'm biased for this next part (since I work on the product) but if you're interested in making your app have abilities like this check out Firebase Remote Config (https://firebase.google.com/docs/remote-config/). While setting up your own config service is not rocket science, having a free one with a web UI is pretty nice.