I would be amazed if you managed to create a map editor for the 4th generation.
I kinda wish I was a programmer, then I could've been able to help and all that.
A 4th generation map editor would have to require reading the models and textures from the ROM. If I am correct... the map editor would also have to require the abbiliy to drag the objects and stretching them. And of course using the textures on the polygons.
Trainer backsprites is actually the next tutorial I have lined up... but between researching it, working on unrelated spriting techniques, and things unrelated to pixel art, I haven't been able to complete it. The most time-consuming part is research and testing; once I'm done with that, the tutorial will go up that same day.
Trainer backsprites are actually handled very differently from game to game, with different art styles to boot, so I have to take that into consideration when drawing the example sprites and explaining my reasoning for drawing them as I do.