I'm just going to list some things I wish the Picture editor had, some have probably already been suggested to you.
* The background image (the white and grey squares) should be able to be relative to the pixel size of the zoom, it would make workig with small art a lot easier. Like, the squares are 4x4 at 4x zoom.
* Being able to pick the transparent color! Being able to draw with it would make work more efficient with being able to just use the Pencil and Ctrl+click in the outside area to get the transparency, and also being able to use the other tools for it to draw translucent pixels (making alpha edges and stuff). Right now only the eraser seemingly is able to do this. And erasing larger areas would be better with the Paint Bucket than the Magic Wand.
* View the alpha image?
* Being able to resize the image along with the canvas.
* I heard you're going to add it, but man do I want to be able to write in the exact numbers for hotspots!
That's quite a few things, but I still felt I had to suggest them. Hopefully you find it feasible!