Look at the Dangerous Rap Trees thread in the General Climbing forum. Note that the insertion of an oversized picture has horizontally bloated the whole thread to the extent that one must scroll sideways to read the text. I don't think this was intentional. In other threads, I've posted cartoon strips that seemed ok on my screen that others found too small. Is there some sort of image coding that will make a posted picture fit exactly into the default width of the thread?
A BBCODE webpage suggests a code substitution [img=wxh] for simply [img], where w and h are the width and height respectively of the image to be displayed in pixels. But might the actual dimensions depend on the browser and/or screen display settings? There's gotta be a way!