I'm personally against putting pre-made identities onto tulpas, think it's better to just let them develop and choose stuff on their own. Especially if it's an identity you're already emotionally attached to, that can make it harder for them to feel comfortable being themself.
You can use an existing character as a base however it should be a loose base and you should allow deviation and go in it with the expectation that your tulpa can and will change from the character you orginally based them off of