How can I set background image from database in css?

How can I set background image from database in css?

How can I set background from database in my case?
obj = UserBackground.objects.get(user=request.user)
bg = obj.image
return render_to_response('template.html', {'bg':bg}....)
template.html:
<div class="wrapper wrapper--home" style="background:
url("{{MEDIA_URL}}{{bg}}") no-repeat center top;">
</div>
style.css:
.wrapper--home {
height: 439px;
margin: 0 auto !important;
}