When you hotlink a photo from another forum, you can see the file name. So, when I right click the mouse on your picture, pull up the menu and click "properties" I get:
Next time, visit the site, right click on the picture and click "Save as" save the file to your computer, then go to www.imageshack.net, upload the file from your computer and then post the link imageshack will give you. The file name will be a bunch of letters and numbers, and people will have to think to get it.