Okay, so I've discovered that a pic's height cannot be changed to anything higher than 200. This made sense during the SCI16 era, where all pics were 320x200. Since the target resolution for the SCI21 template is 640x480, this needs to be addressed. (SCI2 can still support 320x200 resolution, so there's no problem there.)
This naturally results in imported images missing the bottom half. The View editor actually does allow for each view's resolution to be either 320x200, 640x400, or 640x480.