I've been meaning to ask about how the forum handles images. I noted that it put my sonic picture in its own window. That kind of bugs me. But at least that wasn't resized, so it wasn't that bad. But this sucks.
Anything that would stretch out the post or the forum width-wise gets placed in its own scrolling box with SMF. Otherwise, people have to scroll horizontally to read the post, which is bad.
As far as why idol's image was resized, it is because the forum's maximum image height is 768 and the maximum width is 1024. After checking out the image, it is 1200 pixels in height, way beyond the maximum of 768. So the forum resized it.
Some of these restrictions are laid out in the sticky on the general board. If you have huge images, just make them a link. It is the best way.