There are plenty of swan maidens in Narnia and frankly it's a little confusing to Peter--he's more than once made a fool of himself trying to figure out if he's talking to a Dumb swan who is on the large side, Talking swans who might be on the small size, or swan maidens could tend to look identical to Dumb swans. Their human forms are a little more recognizable as they are, on the whole, tend to be pale colored, tall, and beautiful; they also all tend to keep their feathered cloaks on their person at all times, either as actual cloaks or sashes.

What makes them different is if they try to look willowy and delicate--Lucy's two guards look like waifish handmaidens right up until someone tried to hurt his sister, in which case they descended on the attacker with inhuman strength until Lucy would step in to stop them from literally tearing the attacker to shreds--or if they do not.

And, on the other hand, you would get swan maidens like Lady Etain; Peter's new general to the northern armies was taller than most minotaurs he'd met and more muscled too. She looked very pleased when he blurted out as much and said "Some of my fellow swans might try pretty and weak, but they have the same strength as I. I'm one of the ones that are just not going to hide it."

Peter nodded, mainly on the account that he was too busy staring at one of her biceps that was bigger than his own head and coming to the uncomfortable realization that he preferred this brawnier beauty instead.