Four classic player models including all their custom skins (and there are a lot of skins) are available again for installation.
They can be easily installed with the command installmap:

installmap slashbot-classic
installmap martiancyborg-classic
installmap martianenforcer-classic
installmap martianwarrior-classic

After that you can select them in the player setup. For other players to be able to see them, they also need to install these model packs.

slashbot-classic	martiancyborg-classic
martianenforcer-classic	martianwarrior-classic