typo3 backend: show thumbnail in listview

I have a model with the field “image”, which is a simple VARCHAR with the image name. My extbase extension is called ophi_insta and the model is named entry. When I save the image, it is uploaded to uploads/tx_ophiinsta/ and the filename (without the path!) is saved to the database column “image”. What I want is to show the thumbnail of this image beneath the model title in the backend list view. Interestingly enough, this is quite easy: in ext_tables, where $TCA for the model is defined, the following must be added: ‘thumbnail’ => ‘image’

$TCA['tx_ophiinsta_domain_model_entry'] = array(
	'ctrl' => array(
                 .... 
		'thumbnail' => 'image',
                .... 
	),
);

I am honestly surprised that this is working.