Easiest way is fighter factory.
all you need to do is switch the image and group numbers. for instance:
Picture 1's numbers are 0,2
Picutre 2's numbers are 0,3
make the switch and
Picture 1's numbers are 0,3
Picture 2's numbers are 0,2
Make sure you save a backup of the sprite file before you edit. you never know some peoples weird coding until you have already messed it up.