You don't make (pixel) "images" in game. There are maps which are "drawings", possibly containing vector objects (lines, curves), text objects and predefined icons. If you save them locally, they will be XML files, with a syntax similar to SVG (Scalable Vector Graphics). If you give a map to another character in-game, they will see lines, curves, and texts drawn in the same way as everyone, and have the same icons put at the given coordinates on the map.