Since we at GameFreak have decided not to renew the Trainer Customization system outside of skin tone and hair color, we have created a new system for customization:

You can now customize Pokémon: You can put various clothes/accessories on your Pokémon, being anything from pirate hats to T-shirts.

We at GameFreak and Nintendo truly believe that this is the next step forward for Pokémon, and we look forward to seeing all the unique Pokémon!