Here is a perfect example of a clan application.
It's simple, just load bricks, and check out that demolimit save. No one knows its there, so they'll probably think you built it.
Now go around and find whatever neat emitters you can find.
Place a Spawn Point and spawn an item with it, this will show them you know how to make items.
Even if they have no vehicles, and there is already a vehicle spawn in the save, make another one just to make it that much cooler. Remember, the bigger the vehicle, the more impressive the build is.