well the files are saved as .TGAs before they are converted, the original files are all 80.0KB, while mine are 20.7KB. so i don't think that they are too big. also they appear fine in BrawlBox, so i don't think their corrupted.
then maybe delete a bit of extra stuff you won't need (if you never play on hyrule then delete the stgpac)
then it will work
also i haven't done anything with the stages, so i don't know what i would do there.