You can post a picture of it on a thread though. There are 2 ways you can do it.
Directly onto a thread; you will need to host your photos on the internet. First crop and resize your photos to a workable size (~4x5 is good). Then host your photo someplace like (broken link removed) (easy to do). Copy the link they give you. Start a thread or if placing it in an existing thread make sure you are in the advanced mode (get there by hitting "go advanced under the quick reply window or hit Post Reply). Write in your text. Then to place your picture go to the tool bar above the text window. See the icon that looks like a big envelope (not the one with the envelope and paper)? Click it. A small window will pop up to paste your photo link into. When done click OK and your picture should appear in the text box.
As an attachment; You do not need to host it on the web for this method but you will have to size your picture down to 2.00 MB or less to upload them. Once your resized picture is saved scroll down. Do you see the "Manage Attachments" button? Click it. A window will open to add attachments. Browse, find and add your picture. Then click upload. The window will tell you if you picture was accepted or not. If it wasn't you have to reduce the picture more. If it was then you are all set. Once you are done with your message hit Submit Reply and it will appear as a thumdnail at the bottom of your message.
Hope this helps