you need to have some means of loading the graphics into the frame, then some means of storing and loading data. An example would be the text blitter object. You can store tiled graphics in each square of the text blitter in the form of a big sprite sheet, so you can have your game load a sprite sheet at runtime, directly off the computer, then draw sprites on screen according to the values of an array that you can save and load.
U can use array to load and save... U put one object which is the gfx... that object goes throught the grid and pastes backdrops where assigned by the array. I used one object for almost all terrain, it would just changed animations and rnd itself.
I also did for creating objects from the array.
But u should be carefull with the size of the array, try to use as less Z as possible.
The size of my maps reached 5 mb, and loading time in editor bout 5-10 seconds, it was bout 15+ before i upgraded my pc.