You can customize your character in Space Experiment. At the moment there are 4 item categories: clothes, faces , trails and particles. You need to stand next to one of 2 mannequins in the lobby to customize it (You can only customize your character in the Classic Mode Lobby). You can wear up to 3 clothes that you own, paint them and choose one face/particles/trail. You can get these from Crates or Codes.