What type of picture/graphics file(s) are you trying to show and are you trying to post them as attachments or inline? You may not be closing a line and a broken one may not post correctly.

If you tried to change text color, for an example and did not highlight the portion correctly or placed it incorrectly then the results might be NO COLOR or other parts colored that you did not want. Check to see if the /--- tag is placed correctly when you edit. Symmetry is a big plus when you tag so make sure the command terminates where it ought to.

I find it easiest to terminate in the exact opposite order that you activated.

color=red font=Arial Black size=5 FRED SAID HELLO /size /font /color as an example, without brackets so I don't confuse the server. This assures that your post is laid out as you wish and sometimes you'll goof and find your closing tag where it doesn't belong so this might help you learn where to replace it.

Lastly, if you don't have a correct URL for an image, it may not show at all or if you are lucky the server you call will place a file not found image there (like Photobucket or flickr tend to do).