I have found here on stackoverflow a solution to extend django-registration with new fields using signals. Here's the link : http://dmitko.ru/?p=546 .
I have created extended profile model, extended form, added required options to settings , defined urls and the proper form is displayed but only normal User (from auth module) is created. Why is that happening ?
account.models :
from django.db import models
from django.contrib.auth.models import User
from registration.signals import user_registered
import hashlib
class InheritedProfile(models.Model):
    first_name = models.CharField("Name", max_length=50, blank=True, null=True)
    last_name = models.CharField("Last name", max_length=50, blank=True, null=True)
    pid = models.CharField("PESEL", max_length=11, blank=True, null=True)
    street = models.CharField("Street", max_length=50, blank=True, null=True)
    number = models.CharField("Flat/house number", max_length=10, blank=True, null=True)
    code = models.CharField("Zip ", max_length=6, blank=True, null=True)
    city = models.CharField("City", max_length=50, blank=True, null=True) 
    class Meta:
        abstract=True
class UserProfile(InheritedProfile, User):
    def upload_path(self, field_attname):
        filename = hashlib.md5(field_attname).hexdigest()[:4] + "_" + field_attname
        return "uploads/users/%s" % (filename,)
    image = models.ImageField(upload_to=upload_path, verbose_name="Image", blank=True, null=True)
    def user_created(sender, user, request, **kwargs):
        form = ExtendedRegistrationForm(request.POST)
        extended_user = UserProfile(user=user)
        extended_user.is_active = False
        extended_user.first_name = form.extended_user['first_name']
        extended_user.last_name = form.extended_user['last_name']
        extended_user.pid = form.extended_user['pid']
        extended_user.image = form.extended_user['image']
        extended_user.street = form.extended_user['street']
        extended_user.number = form.extended_user['number']
        extended_user.code = form.extended_user['code']
        extended_user.city = form.extended_user['city']
        extended_user.save()
    user_registered.connect(user_created)
I need this InheritedProfile to be abstract as other models will use the same fields.
account.forms
from django import forms
#import strings
from registration.forms import RegistrationForm
from models import UserProfile, InheritedProfile
class ExtendedRegistrationForm(RegistrationForm):
    first_name = forms.CharField(widget=forms.TextInput(attrs=dict(attrs_dict, maxlength=50)), label="First name")
    last_name = forms.CharField(widget=forms.TextInput(attrs=dict(attrs_dict, maxlength=50)), label="Last name")
    pid = forms.RegexField(regex=r'^\d{11}', max_length=11 ,widget=forms.TextInput(attrs=dict(attrs_dict, maxlength=50)))
    image = forms.ImageField(label="Image",)
    street = forms.CharField(widget=forms.TextInput(attrs=dict(attrs_dict, maxlength=50)), label="Street")
    number = forms.CharField(widget=forms.TextInput, label="House/flat number")
    code = forms.RegexField(regex=r'^\d{2}[-]\d{3}', max_length=6, widget=forms.TextInput(attrs=attrs_dict), label="Postal code")
    city = forms.CharField(widget=forms.TextInput, label="City")
and options added to settings :
AUTH_PROFILE_MODULE = 'account.UserProfile'
ACCOUNT_ACTIVATION_DAYS = 7
finally this is how the registration signal looks like :
from django.dispatch import Signal
# A new user has registered.
user_registered = Signal(providing_args=["user", "request"])
EDIT: Indentation of user_created changes nothing until I've tried changing
user_registered.connect(user_created) 
to
user_registered.connect(user_created, sender=UserProfile)
Now I was getting :
"SMTPServerDisconnected
Exception Location:     /bin/python-2.6.1/lib/python2.6/smtplib.py in getreply, line 340 "
Traceback:
File "/home/fandrive/site-packages/django/core/handlers/base.py" in get_response
  92.                 response = callback(request, *callback_args, **callback_kwargs)
File "/home/fandrive/registration/views.py" in register
  47.             new_user = backend.register(request, **form.cleaned_data)
File "/home/fandrive/registration/backends/default/__init__.py" in register
  20.                                                                     password, site)
File "/home/fandrive/site-packages/django/db/transaction.py" in _commit_on_success
  240.                 res = func(*args, **kw)
File "/home/fandrive/registration/models.py" in create_inactive_user
  80.             registration_profile.send_activation_email(site)
File "/home/fandrive/registration/models.py" in send_activation_email
  256.         self.user.email_user(subject, message, settings.DEFAULT_FROM_EMAIL)
File "/home/fandrive/site-packages/django/contrib/auth/models.py" in email_user
  271.         send_mail(subject, message, from_email, [self.email])
File "/home/fandrive/site-packages/django/core/mail.py" in send_mail
  390.                         connection=connection).send()
File "/home/fandrive/site-packages/django/core/mail.py" in send
  266.         return self.get_connection(fail_silently).send_messages([self])
File "/home/fandrive/site-packages/django/core/mail.py" in send_messages
  172.             sent = self._send(message)
File "/home/fandrive/site-packages/django/core/mail.py" in _send
  186.                     email_message.message().as_string())
File "/bin/python-2.6.1/lib/python2.6/smtplib.py" in sendmail
  708.             self.rset()
File "/bin/python-2.6.1/lib/python2.6/smtplib.py" in rset
  438.         return self.docmd("rset")
File "/bin/python-2.6.1/lib/python2.6/smtplib.py" in docmd
  363.         return self.getreply()
File "/bin/python-2.6.1/lib/python2.6/smtplib.py" in getreply
  340.                 raise SMTPServerDisconnected("Connection unexpectedly closed")
Exception Type: SMTPServerDisconnected at /user/register/
Exception Value: Connection unexpectedly closed
Even though I'm using dummy email backend at the moment. Commenting out sending mail function upon registration solved this problem but still my extended user is not created.