Medicine cabinets are either surface mounted or recessed into the wall. A recessed cabinet intrudes less into the room while still providing ample storage, it may look just like a mirror that's been hung on the wall. Service mounted cabinets, on the other hand, or more dominant visually. With either type, style range from elaborately decorated the plain and simple in painted or natural word or metal.
A surface-mounted medicine cabinet can add style to any space, and is one easy way to update a bathroom.
In addition, speciality retailers and architectural salvage shops are a good source for period cabinets. Search Google for "vintage medicine chests" for example, and you can find everything from 1920s era steel chests plated in brass, copper or nickel, to antique Chinese cabinets.