BK..
2 possbile problems.
1. The link is wrong (file is not present at the link)
2. The right permissions for the image, are wrong. (chmod 664 enter)
You can easy see what happans by go here : /var/log/httpd/
Then enter this : tail -f access_log (this will make the log scroll in realtime)
Look for errors there. The same could be done with error_log
Hope this helped.