I’d love to be able to simply provide two icon options to binary switches to define their on/off state without having to create a whole template sensor for the entity.
This. This. This. And so much more of This!
Don’t forget to vote for your own request.
Until you get your feature request, or if you don’t, there are quite a few icon pairs that are predefined in device classes you can apply to your binary sensors (either in their config, or using customize):
I have also made an image of them all here:
However I do realise these do not fit all situations and I think your idea has merit.