Size change and moving shadows are just two.
Size change is well-known and has been studied.
If the image doesn't change, the object must be staying put. Moving shadows have not been systematically studied as an important cue to depth change. If so, we might expect that a moving cast shadow is probably a weak cue which wouldn't overide the changing size cue. By playing the QuickTime movie below, you can observe and verify for yourself the following conclusion. For the green square, the shadow wins.