https://alien-arena.itch.io/alien-arena

Four classic player models including all their custom skins (and there are a lot of skins) are available again for installation.

It's recommended to install all of them at once, because you don't know which ones other players are using. That can be done using the installmodel command from the console inside the game.

installmodel classicmodelpack

You can also install them individually:

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

After that you can select them in the player setup. Important: 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