How can I dynamically change the display format? I have an entityreference field. I want to change the 'Format' under 'Manage Display' from 'Rendered Entity' to 'Label' based on custom logic. Basically, what I'm doing is, if there isn't an image in a node (field_image), it will load a default image from the taxonomy term. If there is an image in the node, it will just display the label. Sorry if this has been answered, but I can't find anything on it. I've tried hook_entity_view_alter, but I don't think that's the right one.
You can do that printing directly the entityreference field in the node.tpl.php. First you need to check if the image field exists and then display the entity reference, so you can do something like this:

if(!$content['field_image']){
   //Load default image
}else{
   print 'Your custom label.';
}


You have to remember to set the format to hidden in the display section.