First, you can only save one map at a time. This map is stored in (%ERME Folder%/maps/map.txt). So if you want to be able to save more than one map, jusy copy it after it is save and rename it to whatever it is to be called. You can use different tilesets with this editor, just make sure you name the tileset, tiles.png, and chnage the number of tiles int the tiles.txt file. (To count the number of tiles, start counting from 0) You can also take the tiles you are using and decrease the size by half to make the thumbnails for it. You would put that image in the media folder and title it tilesThumb.png.