Yes you can post images in your forum posts, as long as they are already uploaded to an image hosting service. You cannot upload images to the jag-stang.com server at this time.
From the forum FAQ:
Can I post images?
Yes, images can be shown in your posts. If the administrator has allowed attachments, you may be able to upload the image to the board. Otherwise, you must link to an image stored on a publicly accessible web server, e.g. http://www.example.com/my-picture.gif. You cannot link to pictures stored on your own PC (unless it is a publicly accessible server) nor images stored behind authentication mechanisms, e.g. hotmail or yahoo mailboxes, password protected sites, etc. To display the image use the BBCode [img] tag.