...But how does the whole replacing stage icons and whatnot on the SSS work? Everything I've tried results in either crashes at the strap loader or crashes at the SSS.
I know nothing about SSS except I think there's a filesize limit. Are you downloading premade icons or are you making your own?
I'm making my own icons and stuff
Replacing SSS icon is possible, I've done it myself quite a few times. But you have to be very careful about the filesize since it's really easy to go over the limit. Try indexing the images with as little colors as possible (without drastically changing the image quality of course) to make the size of the images smaller.
I keep my file size under 1,212,000 bytes. All you have to do to lower to file size is to open you image editing software (i.e Gimp, Photoshop, or something along those lines) and posterize the image to around 20.
Posterizing did nothing but reduce colors from the already reduced colors from indexing. Nothing I do seems to cause any decrease in file size at all, only increase.