Text/small image over top right of featured image

Hello all.

I am working on a real estate website and just want to be able to add a checkbox to each property post so that when it is checked an image or/text appears in the top right of the featured image in all areas of the website.

something like this :

https://img.photobucket.com/albums/v711/zen200/LET_zpsd3b28e6f.jpg

I have been using advanced custom fields for other things, so can I make a check box using advanced custom fields and just have it output the image over the top of any post/page featured image ?

Thanks for any help in advance.