Use skins on offline servers. Supports skins from Mojang API (enter a username to get skin) or mineskin.org.
/skinpls mojang <username>/skinpls mineskin <uuid>
Be warned, this mod is basically a prototype. While it works, it's not polished at all and graceful error-handling is non-existent.
External resources
Project members
sammko
Owner
Technical information
License
MIT
Client side
unsupported
Server side
required
Project ID