Commonly used tiles are 4×4 to 24×24. The tile size is also a design preference however, larger the area you want to cover you might consider using larger dimensions. Most of the interior stone tiles are 12X12 or 18X18, standard thickness is 3/8″ on 12X12 and 1/2″ on 18X18.
We do not recommend tiles thicker than 1/2″ unless you have a concrete floor and have a cement mud installation. Please consult your installer for more information.