/headmodel
The models of Team Arena have interchangeable heads and bodies. If you'd like Gammy's head on Janet's body, all you have to do is use the Janet model and then type the following:

/headmodel *gammy

Note that you must have an asterisk (*) before the head model's name in order for the command to work.

/team_model
This works similarly to the /model command, except that this will set your model for all team games.

/team_headmodel
This command is the team game equivalent of the /headmodel command; it will set your preferred head model for all team games.