title: Django - add image to list display in django admin
body: <p>Please help me. I gave up. I am trying to add additional field to my django admin. I would like to insert image thumbnail there. This is part of my admin.py:</p>
  
  <pre><code>class SiteAdmin(admin.ModelAdmin):
      list_display = ('is_active', 'name', 'description', 'keywords', 'date')
      fields = ('name', 'url', 'category', 'subcategory', 'category1',
            'subcategory1', 'description',
            'keywords', 'date', 'group', 'email', 'is_active')
      readonly_fields = ('date',)
      list_display_links = ('name',)
      list_filter = ('is_active',)
      actions = [activate_sites, deactivate_sites]
  </code></pre>
  
  <p>I wolud like to add 'image' to list_display. Images are generating by thumbalizr. I have a method in models.py:</p>
  
  <pre><code>class Site(models.Model):
      category = models.ForeignKey('Category')
      subcategory = ChainedForeignKey(
          'SubCategory',
          chained_field='category',
          chained_model_field='category',
          show_all=False,
          auto_choose=True,
          blank=True, null=True, default=None)
      name = models.CharField(max_length=70, verbose_name="Tytuł")
      description = models.TextField(verbose_name="Opis")
      keywords = MyTextField(max_length=100, verbose_name="Słowa kluczowe")
      date = models.DateTimeField(default=datetime.now, editable=False)
      url = models.URLField()
      is_active = models.BooleanField(default=False)
  
      category1 = models.ForeignKey('Category', related_name='category',    blank=True, null=True, default=None)
      subcategory1 = ChainedForeignKey(
          'SubCategory',
          chained_field='category1',
          chained_model_field='category',
          related_name='subcategory',
          show_all=False,
          auto_choose=True, blank=True, null=True)
  
      group = models.CharField(max_length=10, choices=(('podstawowy', 'podstawowy'),
                                                   ('premium', 'premium')), default='podstawowy',
                           help_text="&lt;div id='group'&gt;&lt;ul&gt;&lt;li&gt;You can add site to 2 &lt;b&gt;categories&lt;/b&gt;&lt;/li&gt;&lt;/ul&gt;&lt;/div&gt;")
  
      email = models.EmailField(help_text='Podaj adres email')
  
      def get_absolute_url(self):
          return reverse('site', args=[str(self.category.slug),
                                   str(self.subcategory.slug), str(self.id)])
  
      def get_thumb(self):
          host = urlparse(self.url).hostname
          if host.startswith('www.'):
              host = host[4:]
          thumb = 'https://api.thumbalizr.com/?url=http://' + host + '&amp;width=125'
          return thumb
  </code></pre>
  
  <p>It is get_thumb() method. How can I take image to every site and put in in my django admin page? Should I add additional field to my Site model? I don't want to store images on my server - they are directly from thumbalizr.</p>