If you have it set to not allow images in post, then button is still shown to allow them to post the images, but then when the message is displayed, they see the [.img]blah[./img] stuff below is a fix...
in inc_post_buttons.asp replace the line that display's the image with this line...
<% If strIMGInPosts = "1" Then %>
<a href="Javascript:image();"><img src="http://www.eznetideas.com/tools/forum/images/icon_editor_image.gif" width="23" height="22" alt="Insert Image" border="0"></a>
<% End If %>
Brad