Example mezzanine

gistfile1.py

# admin.py:

from copy import deepcopy
from django.contrib import admin
from mezzanine.pages.admin import PageAdmin
from mezzanine.pages.models import Page
from .models import ProjectPage

my_page_fieldsets = deepcopy(PageAdmin.fieldsets)
my_page_fieldsets[0][1]["fields"] += ("thumbnail",)


class MyPageAdmin(PageAdmin):
    fieldsets = my_page_fieldsets

admin.site.unregister(Page)
admin.site.register(Page, MyPageAdmin)

admin.site.register(ProjectPage, MyPageAdmin)

# models.py:

from django.db import models
from mezzanine.pages.models import Page
from mezzanine.core.models import RichText
from django.utils.translation import ugettext_lazy as _

# (example model, excluded irrelevant extra fields for now..)
class ProjectPage(Page, RichText):

    class Meta:
        verbose_name = _("Project page)
        verbose_name_plural = _("Project pages")

# from settings.py:

EXTRA_MODEL_FIELDS = (
    (
        "mezzanine.pages.models.Page.thumbnail",
        "ImageField",
        ("Thumbnail image",),
        {"null": True, "blank": True, "upload_to": "thumbs"},
    ),
)