Since we are on topic of the image editor... will it ever have the option to pick the "invisible" color for a sprite-sheet? It would make life so much easier when you have 1000's of sprites.
The invisible portion is called an alpha channel, and the image editor already supports this. If you create a blank sprite for example, it begins at a 256 by 256 alpha channel, and retains that unless you fill it all.
Likewise, if you set the red, blue, green, and alpha settings on the left side of the editor to 0 each, you have alpha as your "color".
Hope this helps!