When using static files in my Django application, the STATIC_URL is empty even I set it in the setting.py, after a few research, here is how I fixed it.
My static image files are located at movie/static/img (my application is movie)
1. in views.py
from django.template import RequestContext
if you use render_to_response, make sure you add context_instance=RequestContext(request) in it,
render_to_response('movie/index.html', {'movie_list': movie_list}, context_instance=RequestContext(request));