Hmm when people send me PM's sometimes with attachements or when they put a big banner on a forum post it goes massive.
Yes, simply because your forum is very thin, and a wide image will stretch it.
Just like that screenshot is stretching the page here now.
Yes, just make the width wider in the #container section of global.css
Well then use the image resizer plugin. The reason it's stretching is because your forum is much thinner than most forums.
where is the image resizer located?