Changing your username and default album name is not possible.
If you want a different username or default album name, you may open a new Photobucket account by clicking here. You will need to use a different email address for the new account, one that is not currently tied to a Photobucket account. We only allow one Photobucket account per email address.
We do not have a way to transfer the content of one account to another. That can only be done by downloading the images from the old account, then uploading them to the your new account.