If you want something more...modern (I'm not sure what "setting" and "mood" your creperie has, you could try 'Le Monde' by Thievery Corporation(they;re not french, that song is).
Very chill, perfect for a modern setting.
Marie Laforet's version of 'Paint it Black'.
Some french popular music is Johnny Halliday, and more recent: Noir Desir, a rock band. Also, Louise Attaque (try "J't'enmene au vent").
BTW, if you know an artist's name and are trying to find good songs by them, this site is awesome.
http://www.seeqpod.com/music/