Damn it, Deadpool beat me to it.... Anyways, as I was going to say....
Narumi is half right, half wrong... You CAN make new characters and keep up the illusion that it's your custom one, due to the wonderful fact of texture editing. You can make, for example.... Gurney! You can make Gurney look completely different than he was originally.
But if you meant a character model import, no... Not possible atm. (Unless someone has imported a character into Bully)