Aye, to go through all of the pngs would take an immense amount of time, and you have to be careful. If you use some of the tricks for reducing size, Aali's driver has issues with them.
The best way to reduce size is for Aali to support jpeg instead of png for the backgrounds. I asked him about it once and he won't, so that's that. If I ever make my own, I will make the pngs 2x and not 4x.