
Clicking it will open a window where you'll choose the file from your computer, resize it if desired, and hit upload. When you're done the image, hosted by imageshack, will be linked in your reply form, ready to post! In case you do not choose to resize it to something smaller than 640x480 pixels it'll initially show as a thumbnail.
Navigate the tabs on the popup window to upload several pictures simultaneously. This feature also allows you to upload pictures you find on the web (which you can also post by simply copying the link and using the [Img] button). Besides, it has new smilies you can use on the boards.