Yeah, posting pics is relatively easy. You upload them to a photo sharing service like Flickr or Picasa first. I use Picasa. Then, in the web-interface of Picasa, select the picture you want to post. Once it's selected (clicked on), you should see a link that says "Link to this photo". You click on that, then select the "image only" checkbox, and select the size of photo you want. I recommend 400px maximum width.
Once you get that link copied, to your photo hosted at Picasa, come back to the forum and click the icon that looks like a yellow postcard with a mountain on it. Paste your link into that area, and press okay, and Presto! You're done!
For example: