This is a moon themed map, with a large base in its center. It also features a rocket with space inside, an oxygen dispensing unit, (Filled with trees) bunks, alien rebel base, drill and 3 secret holes! There is no barrier around the outside to make the map feel like its really in space! I have tried to make it as packed as possible, but there are still empty spaces. Those areas are just for decoration. It is spacious, has many secret area (easy to find) and plenty of detail. I hope you like it. [EDIT: Added meteorite crash site and telescope! Hope it helps!]
Pretty cool! However, I do agree with @Ares_Xena , you should add more on the outside (like a mini crater or hill) just to fill up the map and add some vantage points for the humans.
With the car idea, at the front I did add a 'rover' (if you have a good imagination) bu a flag sounds cool as well. Thanks for the ideas!
Inside looks great but I also agree with the outside being too empty. Maybe you could add some sort of mining operation outside with a drill going into a crater with ores in it, this would also give you the opportunity to make a mine shaft of some sort that players could hide in branching off of the drilling spot, you could also section off the area with some sort of lunar barrier showing its a construction site. That might look cool also with ore piles too the side showing what the drill collected. Just an idea though you don't have to use it. Glad to help