I gotta agree with John. For the record, it should be noted that GAE used to support non-power of 2 images, and technically, could be modified to do so again, but the entire reason this restriction was added is to hard-force modders to use such images. You see, several older graphics cards are completely unable to use non-power of 2 images, effectively crashing. I don't think the singling out of that (albeit small) minority just to cut a few bytes from the image size is worth it.
GAE is technically capable of doing more advanced HUD stuff than MG, and can match the loading screens, it just has to be done differently. As well, it should be noted that while GAE may not have animated particles, etc, it has a slew of other stuff that balances it out. Finally, as a note, changing the emission rate to a float value (currently an int) as well as allowing animated particle projectiles (the code for animated models is already heavily used; and could also be adapted for tilesets) is reasonably easy, not to mention Will released patches of his changes, so I'm confident that GAE will eventually get around to it, but they've got their arms full with the finishing touches for 0.4, first.