Making custom skins WITHOUT .xnb Converter(s)

In the "...\Pokemon\Content\Textures\NPC"
Step 1 - Rename/Move/Delete the .xnb for the skin you wish to replace.

Step 2 - Copy into the folder the skin as a .png with the respective file-name
(Ex: Hilbert.xnb DELETED > Hilbert.png ADDED)

Step 3 - Launch the launcher and play.

(Note: Sometimes when an .xnb overlaps a .png in-game, the .png might flash.)