Add functionality for wrapping text around images. This could be through adding an 'align=left/right' option to the existing [img] tag, an [imgwrap] tag, or just through allowing the use of table tags.
It's nothing to do with resizing, it means its literally impossible to put text to the side of images. Table tags are a common BBCode element, and they even work in the current post editor, they just aren't rendered by the forum. I think tables would be a useful thing to have in their own right, TBH.