Ears are extremely expressive!
Generally, if they are not perfectly symmetrical, the dog is relaxed.
Dog body language generally depends on a combination of parts. For instance, wide out to the side can mean relaxed... unless the brow is furrowed (which I find extremely hard to see on yorkies), which means the dog is worried. If you knit your brow, you can kind of feel your scalp move around your ears and sort of feel how a dog would make a worried expression, which I think is pretty cool.