As Ilwan said. The export settings can be found by going to the TOOLS drop down menu, OPTION -> BMP, PEG, PNG (a button), to get the area where you can define how big an image will be. Then use the SAVE AS... option and I usually use the PNG RECTANGULAR image. Every single one of my DUNGEON maps for Thunderspire, Pyramids of Shadow and Trollhaunt maps were saved this way.