Usually send_mail() will suffice for most emailing functionality, but when you need to attach something, the helpful Django wrapper function won't allow it.
If you need to add attachments to your emails, you'll have to go deeper.
Alright, down to the nitty gritty.
from django.core.mail.message import EmailMessage
email = EmailMessage()
email.subject = "New shirt submitted"
email.body = html_message
email.from_email = "ThatAwesomeShirt! <firstname.lastname@example.org>"
email.to = [ "email@example.com", ]
email.attach_file("hellokitty.jpg") # Attach a file directly
# Or alternatively, if you want to attach the contents directly
file = open("hellokitty.jpg", "rb")
email.attach(filename = "hellokitty.jpg", mimetype = "image/jpeg", content = file.read())
And that is all folks.