Seems you figured it out, but just in case:
- Click where it says "embed this image"
- copy the link where it says "forum" (looks like this: )
[URL=http://imageshack.us/photo/my-images/846/bankotsufull770245.jpg/][IMG]http://img846.imageshack.us/img846/3921/bankotsufull770245.jpg[/IMG][/URL]
Uploaded with [URL=http://imageshack.us]ImageShack.us[/URL]
- Delete everything except the [IMG] wraps and the link inside
- should look like this (but without spaces):
[IMG ]http://img846.imageshack.us/img846/3921/bankotsufull770245.jpg[ /IMG]