If/When Mars or the moon are colonized, transport will be needed between bases. Over long distances, rovers would be too slow and traditional aircraft would not work well in thin to non existent atmosphere. Obviously due to low gravity the rocket could be quite small with a non traditional design. Perhaps similar to the apollo lunar module?
The energy, material and safety costs of rocket flight on the moon probably mean most bulk cargo will travel by some form of surface transport.
For those cases where use of a rocket is justified some work has been down on exploiting in situ Aluminum, reacting with Oxygen or Water. The water option appears more stable and easier to handle than cryogenic oxygen, but involves water which may be more useful as life support and has a performance loss due to the energy involve in liberating the hydrogen.
The suggested performance for oxygen/aluminum seems to have an ISP of around 200, giving fuel loads of between 50% and 70% depend on how 'orbital' your planned route is, so in terms of what the craft looks like, it is going to be at least half tankage, exact nature of that tank will depend on how the Aluminum is stored and handled noting that getting the predicted performance seems to be complicated where the aluminum is in solid or powder form- the logistics of fueling and servicing a craft with one tank of liquid oxygen and the other liquid aluminum seems excessively exciting.
One note with any aluminum based rocket is that it will tend to produce solid particulate as exhaust at very high velocities, which probably cannot be allowed to routinely impact solar panels or similar habitat structures, suggesting that any launch facility will need to be carefully positioned.