How much planetary-surface detail might one be able to observe without resolving an exoplanet? Simulations of Light Curves from Earth-like Exoplanets - Planetary Habitability Laboratory @ UPR Arecibo. I have expanded those simulations to include other big Solar-System objects. They were done with the Sun over the equator and the observer looking toward the body from the Sun's direction. Maps were from NASA's Blue Marble site for the Earth, Eclipsophile for the Earth's clouds, and the Celestia Motherlode for all others. I assumed Lambert-law reflection for simplicity.
Venus, Jupiter, Saturn, Uranus, and Neptune are clouded over, and they have very little change, about 1% for Jupiter.
Of the exposed-surface bodies, I find these relative standard deviations. Mercury: 2%, Earth: (red: 12%, green: 11%, blue: 2%), Moon: 16%, Mars: 10%, Io: (red: 5%, green: 7%, blue: 11%), Europa: (red: 5%, green: 8%, blue: 10%), Ganymede: (red: 6%, green: 5%, blue: 8%), Callisto: 10%.
So the Earth, the Moon, Mars, and Jupiter's four big moons all have noticeable asymmetries. For the Earth, the Moon, and Mars at least, these are due to geological activity. The Earth even changes color. For most directions of the Sun and the observer, the Earth is indeed a pale blue dot. But when the Sahara Desert is illuminated and visible, it is big enough, light enough, and yellow enough to make the Earth look grayish.
So if one can directly detect a terrestrial exoplanet, one may be able to tell if it has geological activity. One may also be able to tell if it has an ocean that covers much of its surface but not most or all of it.
This is important, not only in itself, but also for whether there is life on other planets. This is because the most plausible locale to date for the origin of Earth life is in a hydrothermal vent, and hydrothermal vents require geological activity and bodies of water to exist.