—Nos sonaba tu cara.
 

—Nos sonaba tu cara.

Is this a common expression?
I haven't found a reasonable translation.

"Sonarle algo a alguien" means that something is familiar to someone.

- Me suena el nombre, pero no recuerdo de dónde lo conozco.
The name rings a bell, but I don't remember where I met him.

- Nos sonaba tu cara.
We'd seen your face somewhere before.

- No me suena ese actor, ¿cómo se llama?
I'm not familiar with that actor, ¿what's his name?

- ¿Dices que no te suena esta foto? ¡Pero si es famosísima!
So the photo doesn't ring a bell with you? But it's so well known!

Totally agree with Angelica.

Oxford bilingual also gives examples,

(resultar conocido)

me suena tu cara — I know your face from somewhere

¿de qué me suena ese nombre/esa canción? — where do I know that name from/that song from?

me suena haberlo oído antes — it rings a bell / it sounds familiar

¿te suena este refrán? — have you heard this proverb before?

https://es.oxforddictionaries.com/tr...-english/sonar

Thank you, makes sense when you look at it from that angle.