I'd find it really handy to have a free transform tool for images (and curves). I'm using a lot of images in my work, and very often need to apply some perspective and distortion for image correction, or applying unique style to the assets.
I think the best way would be to have just the bounding box 4 points editable as it it were a square shape in the node editor, then the shape would just fit to the modified bounding box.
Should I add such a request in the bug tracker?