If we confine ourselves to only the surfaces of planets and minor bodies, the answer is virtually all of the surface area in our solar system has been mapped at least at some resolution. The Planetary Cartography Working Group has identified over 1.9 billion square kilometers of stable surfaces in the solar system, not including the atmospheric features of Jupiter, Saturn, Uranus and Neptune, and of this total, all but a few percent have been mapped at resolutions of 10 - 100 meters or lower. Some surfaces such as the Moon and the Earth, have been mapped at substantially higher resolution.
This means that there are very few surprises left for us to 'see for the first time' in this solar system. Now comes the hard job of geophysically and minerologically assaying these surfaces to determine their chemical composition and how they got to be the way they are!