If you use MCCustomSkinLoader, here is an offline-mode Minecraft skin server using CustomSkinLoaderAPI.

NOTE: It's only for offline-mode server. Anyone can chang the skin while knowing the player's ID.

REQUIREMENTS

JDK(JRE) 1.8

USAGE

Just run the jar.

java -jar mc-customskinloader-server-0.0.1-SNAPSHOT.jar

The default server port is 80. So you can visit http://{your ip} to upload your skin textures.

Add the server to ExtraList, and enjoy your game.