You could add in some events to move the camera around and take screenshots until you have screenshots of each part of the entire layout and then stitch those screenshots together to make a map of the entire level at the highest quality.
I suppose you could do that manually within the editor as well.
Otherwise, I don't know of any way to get an image of the entire layout at full resolution.
Oh god D: But most of the maps are 1792, 1400; and the hub area is 5000, 5000! Now, suddenly, my game seems VERY big. Help me pleeeaaase, someone