The current SugarFeed display code uses the defunct “picture” field to attempt the display of the user image instead of the “photo” field (which needs to be added to the viewdefs instead of “picture”).
To fix change line 405 of SugarFeed\SugarFeed.php from:
$image_url = 'index.php?entryPoint=download&id='.$user->picture.'&type=SugarFieldImage&isTempFile=1&isProfile=1';to
$image_url = 'index.php?entryPoint=download&id='.$user->id.'_photo&type=Users';