The whole point of meditation is to allow the subconscious to "take over" from the conscious.
The conscious Mind sees and hears what you want to see and hear. The subconscious sees and hears everything! Everything you have touched, everything you smell. Every action you have ever taken is registered by the subconscious. So, yes, you are bound to see, sometimes, faces that your subconscious has seen, but that you never noticed. It can sometimes be quite scary! But don't stop meditating because of these "visions".In meditation there is a vast amount of knowledge that you can "tap into". Don't be afraid! Magic awaits you!