Trevor some common mistake when trying to post pictures is to get [img]and[/img] backwards the "/" ends the command so make sure it is after the URL. Also the URL must contain the "HTTP://" at the beginning. example: http://www.domainname.com/graphics/picture.jpg (Not a real picture). And make sure there are no spaces between the image commands and the URL.
If you need further guidance I'll be more than happy to further confuse the issue.