By using a simple command you can change the character model and respective voice that you use mid-game instead of just before joining a game. The command is usable in both online and offline modes via the console. Unfortunately, you cannot change to a character skin that you do not own.

Step 1) Install League of Legends
Step 1) Join a game
Step 2) Open the console by pushing tilde (`) above your tab key
Step 3) Type in "ChangeCharacter SkinNameHere" and hit enter
(ex: ChangeCharacter Corporal_Lewis)

Congrats, you've changed your portrait and voice.

Your character model will update to others when you're out of their sight, and will update for you when you suicide or get killed.

Below is a list of the skin names, organized by release date/pack.

Corporal_Lewis








Lieutenant_Masterson








Police_Constable_Briar








Police_Sergeant_Davin








Private_Schnieder








Sergeant_Powers

Agent_Wilkes








FoundryWorker_Aldridge








DJ_Scully








Dr_Gary_Glover

Mr_Foster








Security_Officer_Thorne








LanceCorporal_Lee_Baron








Mike_Noble

Harold_Hunt








Kerry_Fitzpatrick








Trooper_Clive_Jenkins








Paramedic_Alfred_Anderson

Chopper_Harris








Kevo_Chav








Captain_Wiggins








Reverend_Alberts

Steampunk_Berserker








Steampunk_Firebug








Steampunk_Medic








Steampunk_Sharpshooter

Steampunk_DJ_Scully








Steampunk_Demolition








Steampunk_Support_Specialist








Steampunk_Commando

Dave_The_Butcher_Roberts








Dr_Jeffrey_Tamm








Samuel_Avalon








Shadow_Ferret

Harold_Lott

ChickenNator

DAR

Reggie

Harchier_Spebbington








Pyro_Red








Pyro_Blue








Baddest_Santa








Steampunk_MrFoster








KF_German








KF_Soviet








Commando_Chicken








Ash_Harding








Reaper








Ricky_Vegas








Hayato_Tanaka








Steampunk_Mrs_Foster








Harchier_Spebbington_II








Ms_Clamley

Voltage








Mr_Magma

Mrs_Foster