You should be able to post an image in your profile. Your avatar, the picture that appears under your user name, should be easy to load.
If you're talking about posting an image in the forums, you might not have permission to do that. It requires 50 posts before you can post a "live" link, otherwise it will just show up as a website link.
Check here for any more questions on posting images:
http://www.runecrypt.com/forum/index.php?showtopic=3743