The following assumes that you're using the inbuilt save scene. I don't know much about BlizzABS and whether or not it changes the save scene.
I think that in your Window_SaveFile script, you'd have to find this bit of code and tweak it according to however your facesets are defined:
# Draw character
for i in 0...@characters.size
bitmap = RPG::Cache.character(@characters[i][0], @characters[i][1])
cw = bitmap.rect.width / 4
ch = bitmap.rect.height / 4
src_rect = Rect.new(0, 0, cw, ch)
x = 300 - @characters.size * 32 + i * 64 - cw / 2
self.contents.blt(x, 68 - ch, bitmap, src_rect)
end
For example you might change the line
bitmap = RPG::Cache.character(@characters[i][0], @characters[i][1])
into something like
bitmap = RPG::Cache.picture(@characters[i][0])
if your facesets are stored in the Pictures folder and have the same name as the corresponding character sets.
I haven't tested this but I hope it helps >_<''