The "SKIN" folders simply contain replacement image folders for the player character.
By copying these images over the original images in the same respective folders in the
PlatformerPack folder, you'll change the appearance of your character.

This is NOT the same as the "character map" feature in Spriter.  If you want to use
character maps to allow yourself to change the appearance of your player character
between the diferent skins, you would first have to rename each of the sub-folders in
each skin folder,for example renaming "head" to "girl_head" or "cat_head" etc. and then
add these newly named folders to the PlatformerPack folder.  Then you'd need to create
the actual character map in the .scml file using Spriter, to make Spriter swap out the
default grey guy body part images with the alternate "skin" body part images.

For more info on character maps, please reference the built in manual by choosing help/
help from Spriter's main menu.

Thank you for reading.