You can have huge arrays if you need to, but don't use them to store data that is dumped from bitmaps, etc. I wouldn't create a ship of 32x32 "pixels" - better use a smaller sized "sprite" (array) and scale it bigger.

"Is it allowed to create save-files and reload them? Or an editor that can create and reload files?" Yes and yes, if you create the saved data at runtime. Don't use previously saved data with your project.

You can save your procedurally generated sprites in the game folder and use them from there; however, the demo kit should not contain the sprites.