model.py

from __future__ import unicode_literals
import os
from uuid import uuid4
from django.db import models

def file_image(instance, filename):
    ext = filename.split('.')[-1]
    filename = "%s.%s" % (str(uuid4()), ext)
    return os.path.join('upload', filename)

class Karyawan (models.Model):

    nama = models.CharField(max_length=100)
    alamat = models.TextField(blank=True)
    foto = models.ImageField(upload_to=file_image, verbose_name='Photo', null=True, blank=True)

    def __unicode__(self):
        return self.nama