OfflineSkins – mod allows you to download skins that you use online, without access to the Internet.
OfflineSkins Mod for Minecraft 1.13.2
Put your skin in the next folder – “.minecraft / cachedImages / skins” and name the skin your nickname. Thus, the mod will use this skin for all your characters, even in offline mode.
Download Link: OfflineSkins_1.13.2_v1a