You can really use any bread your heart desires! Whether that be a sourdough baguette, or a country loaf. I love a good sourdough, so I generally gravitate towards that, but sometimes I'll use a sesame wheat loaf as well, which is just as good. Using stale bread here is also a great way to use up old bread that would otherwise go in the garbage to make your croutons! My one note for bread is to not use any bread that is too soft, it won't crisp as much and provide the crouton crunchy vessel you need for your caesar, it will get soggy too fast with the dressing.