yourwebsite.com/forum/images
basically the root folder of your forum.
Goto your forum, usually you will see,
www.mysite.com/forum/ or
www.mysite.com/forums/
Then image folder is in the directory forum or forums ( dependant on what you have )
If your still stuck..and maybe have a custom style.
A quick method to determine where your image will reside is to right click your forum logo. Click properties.
Ste
reuploaded info and image