event-timeline/app/media/models.py

from django.conf import settings
from django.db import models
from django.urls import reverse


class Image(models.Model):
    created = models.DateTimeField(auto_now_add=True)
    modified = models.DateTimeField(auto_now=True)

    file = models.ImageField(upload_to='image', null=True, blank=True)

    def get_absolute_url(self):
        return '/' + settings.URL_PREFIX + self.file.url[1:]
    get_absolute_url.short_description = 'URL'

    def image_tag(self):
        from django.utils.html import mark_safe
        return mark_safe('<img src="%s" style="max-width:256px" />' % self.get_absolute_url())
    image_tag.short_description = 'Preview'

    def __str__(self):
        if self.file:
            name = self.file.name.split('/')[-1]
        else:
            name = 'None'
        return name