+" is for multiquote.
Allows you to quote multiple posts in one reply. go to a thread, click on a few of them, and then click 'Post Reply' . The next page will have all of the quoted posts that you marked
To add a pic to your quoted replies, click 'POST REPLY' button insted of using the 'Quick Reply' box at the bottom. There you can either add an image that is hosted, or upload a pic as attachment